Category Archives: Blog

Why no sparrows?

Sunrise in the scrub. Forest Road 46, Ocala National Forest

May 10, 2014

I find being in big expanses of native habitat around sunrise has the effect of producing brief moments of clear-headed thinking. For me, this is especially true of the more open habitats, like early stage scrub, where you can easily track the incremental effects of the ascending sun as the surging morning light progressively highlights newly visible features of the environment. I was sitting in just such a dense patch of oaky scrub in the Juniper Prairie Wilderness area of Ocala National Forest on Wednesday when one of those rare moments of lucidity raced through my normally muddled brain. I kid you not that I was actually sipping my tea when I heard the clear whistle and trill of drink-your-tea coming from the dense scrub. At that moment, I realized that I had made a foolish and easily refutable claim in my last post, in which I pondered the absence of breeding sparrows in most Florida habitats. I claimed that for the most part Bachman’s sparrow was the only breeding species in most inland or upland habitats of the Florida peninsula.

As it turns out, Bachman’s sparrow isn’t the only widespread breeding sparrow in the Florida peninsula.

Astute birders and natural historians no doubt immediately recognized the fallacy of that statement – there’s one species of sparrow that breeds in a variety of habitats in peninsular Florida, and can be incredibly abundant in some, including scrub. Towhees are sparrows, really. We just don’t call them sparrows. A bit larger and more conspicuous in plumage than the typical cryptically-hued sparrow-type sparrows, but members of the same family (Emberizidae) nonetheless, and classified within that family as belonging to the same clade as the New World sparrows. In most respects, their ecology is similar to that of the smaller sparrows – they are omnivores, feeding more on seeds and plant-derived foods during the fall and winter, and switching to more of an animal-based diet during the breeding season when their voracious offspring need more protein than is available in most plant foods. They are fond of open or early successional habitats, though in Florida they nest in open-canopy woodlands like flatwoods or scrub as well. Eastern towhees were by far the most common breeding birds I heard in most areas of the Juniper Prairie Wilderness scrub on this beautiful May morning.

Drink your tea, he said. I was way ahead of him.

The juvenal plumage of eastern towhees clearly shows their affinity to sparrows.

So we do have a common breeding sparrow in many peninsular Florida habitats. But that doesn’t really resolve the conundrum – in some ways it magnifies it. If this one species of emberizid can successfully maintain viable populations here, why not the other sparrows with which it frequently co-occurs in breeding bird communities further north? It’s not hard to find towhees nesting along with other species typical of the shrub-sapling stage of old field succession, such as song and field sparrows. The enigma is further confounded by the fact that field, song, grasshopper, chipping, swamp, and several other rarer sparrows (Henslow’s, LeConte’s, Lincoln’s) can be found wintering in these habitats in Florida. But none stay to breed. Why not?

Field sparrows winter in peninsular Florida, but don’t stay to breed here.

The sparrow problem is just one component of the riddle of peninsular Florida’s low breeding bird diversity. One of the most well-documented trends in landscape ecology is the profound latitudinal gradient in species diversity among a wide range of taxa – as you move from the temperate zones towards the tropics, the number of species of many, many groups of organisms increases dramatically. Though this pattern is widely known, it hasn’t been clearly explained in terms of an underlying cause or mechanism. More than a dozen hypotheses have been suggested to explain the higher diversity in the tropics, but none is universally accepted, and in fact most of the hypotheses are not even mutually exclusive. Like many complex ecological phenomena, the origin of these diversity gradients is probably multifactorial, arising from a number of interacting factors and causes. Higher productivity, greater climatic stability, a longer evolutionary history, greater importance of biotic interactions such as competition, predation, and parasitism – all of these and many more may contribute to the higher tropical diversity. But despite the fact that Florida is at a lower latitude than most of North America, and might therefore be expected to have higher bird diversity than areas further north, at least for breeding species of land birds that isn’t true. The picture with respect to breeding bird diversity in eastern North America is more complex and perplexing.

Number of breeding land bird species in North America, from a paper by Cook (1969).

The figure above, originally published in a 1969 Systematic Biology paper by R.E. Cook, contains a wealth of head-scratching trends in diversity. I first saw this figure in Eric Pianka’s classic little book Evolutionary Ecology over 30 years ago, I think, and it has taunted me ever since. This map shows the number of breeding land bird species in 300-square mile blocks, and even at this crude level of resolution, the contradictions and puzzles are enough to make me swoon. If you focus on the numbers of species breeding in the middle of the continent, starting in the prairie provinces of Canada and working towards Mexico and Central America, the temperate-tropical diversity gradient is apparent. But to the east, something funky is going on. Diversity actually is greatest at higher latitudes. In particular, notice the column of blocks that includes Florida – there are 141 breeding species in the region of the Great Lakes, but in the southeast block that includes Georgia and North Florida, there are only 93 breeding species. Though there is no number for the block that contains peninsular Florida, by my reckoning that number is about 72. I’ll repeat my previous claim – breeding bird diversity of land birds in the Florida peninsula is abysmal relative to the rest of eastern North America.

The reduced numbers of species of some taxa in Florida has been explained at times by the so-called peninsula effect. For a variety of types of organisms, peninsulas often show reversed diversity gradients from base to tip, though the mechanism for this trend is difficult to pin down. One component for some organisms may have to do with the colonization and extinction dynamics of populations in the peninsula (I’m referring here to extinction of individual populations in an area, not an entire species). Because peninsulas have less direct connectivity with nearby land areas that may serve as a source of colonizing organisms, they may lack populations of species with poor vagility that are unable or unlikely to reach the more distant parts of the peninsula. Further, smaller extents of appropriate habitats in peninsulas may support smaller populations of the organisms that do manage to colonize, producing higher extinction rates for these populations. Finally, the range of habitat types may be reduced in peninsulas, preventing some species from colonizing in the first place. With respect to birds, the colonization argument just doesn’t work. Many of the bird species whose absence as breeding birds puzzles me migrate through or winter in the peninsula in large numbers, so getting here isn’t the problem. The population size and habitat availability arguments may contribute to Florida’s low breeding bird diversity, but they aren’t the whole story.

Northern parulas are abundant foliage-gleaners of hammock habitats, but other warblers and foliage-gleaners typical of forest habitats further north are absent.

For both islands and peninsulas, greater land area is related to greater species diversity, called the species-area effect. That may explain some of Florida’s lower breeding diversity, but not all of it. Look at the number of breeding bird species in the block that includes that little sliver of land called the Isthmus of Panama – it has around 600 breeding species! Land area isn’t everything.

One of the problems with the peninsular effect as an explanation for Florida’s low diversity of breeding birds is that this reversed diversity gradient of breeding birds isn’t restricted to the Florida peninsula – it is general to the southeastern United States. But even so, many bird species common as breeders in the southeast don’t make it into the peninsula. There’s something else going on here. One of the proposed explanations for reduced densities and diversity of breeding land birds in the southeast is related to the dynamics of primary productivity in temperate habitats. Simply put, temperate habitats further north experience a much more concentrated burst of plant growth in spring as all of the dormant vegetation begins leafing out around the same time, providing huge amounts of tender nutritious leaf material for herbivorous invertebrates. This burst of productivity works its way up the food web, resulting in a glut of food for the breeding birds. Spring certainly brings a burst of new growth in Florida, but probably not as dramatic and concentrated in time as in more northerly habitats. One factor contributing to this reversed diversity gradient among forest bird communities of eastern North America, which benefit hugely from this spring burst of productivity, is that more northerly bird communities show show both decreased extinction rates of individual species in the community, and lower turnover rates in community composition (number of species that disappear or appear between years). Stated another way, more southerly populations of these forest-breeding birds are more likely to disappear over time, and more likely to be replaced by other species.

Red-eyed vireos are far more abundant in migration than as breeders in peninsular Florida

The breeding bird communities of peninsular Florida’s broad-leaved forest habitats (hammocks) have always struck me as being particularly depauperate. Northern parulas are usually abundant, but other species of foliage-gleaning warblers are hard to find. There are no ground-foraging forest warblers breeding here at all, though ovenbirds are common in migration in these habitats. Red-eyed vireos, one of the most abundant breeding species of eastern deciduous forest, are present as breeders in many Florida hammocks, but at much lower densities than further north. It seems to me that both the productivity burst effect and area effects may be at work here. Many of the characteristic tree species of hammocks are evergreen; even though these species do put out new foliage in the spring in a leaf flush (live oaks, for example), the boom-bust nature of the resource experienced by birds breeding in forest habitats further north is not as dramatic here. In addition, hammocks themselves tend to be more patchily distributed and limited in area than do deciduous forest tracts in eastern North America. Smaller extents of habitat support smaller populations, which are more likely to go locally extinct, and exclude wide-ranging species that need large expanses of appropriate habitat in order to maintain viable populations. Hammock habitats in the peninsula are actually probably far more extensive now than they were historically; fire suppression in some formerly extensive habitats has resulted in expansion of fire-intolerant hammock habitats in many areas that once supported vast tracts of fire-dependent plant communities like sandhills and scrub.

Hammocks are historically patchily distributed habitats in peninsular Florida, but have expanded greatly due to fire suppression.

Other forest breeding guilds (a guild is a group of species that use similar resources in a comparable way) besides the foliage-gleaning warblers and vireos are equally perplexing. Tyrannid flycatchers, for example. Eastern deciduous forests further north typically support several species of forest-breeding flycatchers, including great crested flycatchers, eastern wood pewees, and Acadian flycatchers. We have lots of great cresteds, but Acadian flycatchers and pewees become harder and harder to find the further south you go in the peninsula. It’s tempting to suggest competition with insects as a possible link to the lowered diversity of breeding flycatchers in Florida – the superabundant and diverse dragonfly community must to some degree reduce the resource base, flying insects, on which tyrannids depend.

Do dragonflies, which presumably compete with flycatchers for aerial prey, reduce diversity and density of tyrannids in Florida?

Great crested flycatchers are common breeding birds in Florida, despite any competition from odonates.

Other forest tyrannids, like this Acadian flycatcher, are scarce as breeders.

But none of those explanations seem to fit the sparrows. Most sparrow species in eastern North America are characteristic of disturbed or successional habitats – song, chipping, field, grasshopper, and so on. Successional or disturbed habitats by their nature are patchy in distribution, often limited in areal extent, and prone to disappearance over time as they are replaced during the process of secondary succession. Superficially, an old-field habitat in Florida is remarkably similar to one in Virginia, except that breeding bird diversity and density is dramatically lower. Examine the breeding density maps prepared by the U.S. Fish and Wildlife Service (http://www.mbr-pwrc.usgs.gov/bbs/bbs.html) for any of the missing Florida breeders. I’ve pasted these breeding density maps below for four species: song sparrow, field sparrow, chipping sparrow, and eastern towhee. The low breeding abundance or complete absence in peninsular Florida of the three “typical” sparrows is apparent, and in marked contrast to that of the towhee, which actually shows increased breeding abundance in the central-southern portion of the Florida peninsula.

Song sparrow, a common winter resident that doesn’t breed in Florida

Song sparrow breeding abundance

Field sparrow

Field sparrow breeding density

Chipping sparrow

Chipping sparrow breeding density

Does the smaller burst of insect productivity in spring prevent species like this field sparrow from successfully raising young here?

Florida race of the eastern towhee, Pipilo erythropthalmus alleni.

Breeding density of eastern towhees. Why are they so much more successful in the southeast than other sparrows?

So towhees love Florida, even though the productivity burst model may affect Florida towhees to some degree as well. Eastern towhees in Florida show the same shift in diet between winter and spring as do more northerly populations; they switch from a greater reliance on plant-based foods in the winter to more animal prey in the spring and summer. However, the magnitude of the shift is of a lesser magnitude in Florida towhees, who rely more on plant-based foods during the breeding season than do northern populations, perhaps hinting at a lower availability of insects in the Florida habitats used by towhees as well.

But what is it about towhees that makes them so successful in Florida, while all the other sparrows of similar habitats hightail it north in the spring? I’m still awaiting enlightenment.

Reference: Cook, R.E. 1969. Variation in Species Density of North American Birds. Systematic Biology 18 (1): 63-84.

The saddest season

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April 27, 2014

Thursday last week, I saw my first bobolinks of the season, in the marshes of the Tomoka River near Tomoka State Park. Several flocks of 30-40 birds were winging across the marsh, with occasional dink notes. It was the calls that first made me aware of them. I saw more bobolinks on Saturday – a flock of perhaps 100 birds or so flying over the marshes and impoundments of Emeralda Marsh Conservation Area.

Bobolink males at Lake Woodruff NWR

Bobolinks are probably my most anticipated spring migrant, at least among the species that I see reliably every year. When I read the listserve reports of amazing warbler lists being tallied at Ft. DeSoto and some of the Brevard County sites, I suffer from severe attacks of envy, and in those moments have dozens of new most-anticipated species. But I have yet to see a Swainson’s warbler, after decades of birding, so snagging that one doesn’t appear to be imminent. But I do see bobolinks somewhere every year, and that almost makes up for the more glamorous stuff I can’t make myself drive hundreds of miles to see.

Seeds are a major food item while bobolinks are migrating.

But bobolinks count for a lot. It’s a pity we get to see them for such a short time each year; they are very interesting little blackbirds. Bobolinks are devoted seed-eaters; the epithet in their latin name Dolichonyx oryzivorus explicitly references their fondness for grain crops (oryzivorus = rice eater). The color pattern of males in breeding plumage is splendid and rare, one of the relatively few species of birds to exhibit reverse countershading, in which the upper surface is more brightly colored than the underside. The more typical countershading places the darker hues on top and lighter below, which is hypothesized to make them less apparent in a top-lit environment. Reverse countershading does the opposite – it makes the bird stand out against its background. Not surprisingly, bobolinks show a high degree of sexual dichromatism – the females are predominantly a lovely straw-colored yellow-brown, and so are the males during the non-breeding season. The highly apparent colors of the male are coming in while bobolinks are in Florida – some males still show signs of molt going on.

Male bobolink showing a trace of basic (winter) plumage in the belly feathers.

Female bobolinks are more subtle than males, but equally beautiful.

The reverse countershading of a male bobolink in alternate plumage makes them very conspicuous in open environments, like the grasslands where they breed.

Their extreme sexual dichromatism may be related to their breeding system, another unusual component of their life history. The majority of passerines are monogamous, but bobolinks are one of a number of blackbird species that practice polygyny, at least occasionally. Some males have multiple mates, usually 2 but ranging up to 4. The quality of a male’s territory is probably a big factor determining which males get multiple mates while others are monogamous, but you have to figure the visual displays of the male play some part. Quite likely, the two traits are correlated – males with brighter plumage probably also have better territories and other qualities of interest to a discriminating hen bobolink.

Bobolink males arrive on their breeding grounds before females to stake out the best territories, and maybe get a second mate.

What I love most about bobolinks though is their exuberance for life. They seem to almost always be on the move, with definite places to go to in mind. Most of my sightings of bobolinks are of flocks in transit, and my views of them are cruelly brief. But every now and then I get to see a group working methodically through an overgrown field or marsh, birds in the rear of the group constantly leap-frogging those near the front. And if I’m really lucky, I get to hear a big flock in which the males are singing. The song of the bobolink is one of the most rollicking, joy-filled vocalizations of any bird I’ve actually experienced. How’s that for egregious anthropomorphism?

As much as I love seeing bobolinks when they finally appear in late April, they bring mixed emotions. They are the tail of the progression of migrants that has snaked through the peninsula in the previous several months. And as the last stragglers of those transient migrants finally leave Florida by the second week of May or so, an ugly and inexplicable fact hits me in the face again every year – Florida’s summer bird diversity sucks. Okay, so that’s a massive overstatement – even at its worst, Florida’ avifauna is always amazing, but it reaches its nadir of diversity in mid-summer. And preceding that low point, all through the latter half of spring, diversity and abundance of birds generally follows a protracted and depressing downward slide.

What makes this vexing to me is that it is exactly the opposite of the seasonal patterns of bird diversity for birders in most of North America. At a time when most birders are enjoying a dramatic increase in abundance and diversity, Florida birders have to wait until fall migration begins in mid-summer for avian diversity to begin to climb. Bird species richness reaches a peak in Florida in late-winter to early spring, and then crashes in late spring, in the last week of April and first week of May. The graph below shows the severity of the decline in diversity – these data were collected over the course of 7 years of surveys at Emeralda Marsh Conservation Area in Lake County, and though they don’t represent the entire range of inland habitats, they are a pretty accurate representation of changes in diversity in peninsular Florida.

Seasonal changes in the number of species seen per census at Emeralda Marsh Conservation Area.

This decline in diversity isn’t limited to any one specific group of birds – it’s a general phenomenon among many taxonomic groups. The graphs below show the seasonal changes in diversity for 2 taxonomic divisions – passerines (Order Passeriformes, the perching birds) and non-passerines (all other orders), and the difference in the overall pattern between these two groups is minimal. Breeding diversity for most taxa of birds that occur in Florida is at a minimum in the summer.

The decline in diversity in spring is a bit more drastic for passerines, but in general most bird taxa show the same patterns.

Every spring after the semester ends, I drive to northern Virginia to visit my dad for a week, and spend as much time as I can in the glorious Virginia countryside when bird breeding activity is kicking into high gear. The difference between Virginia and Florida in both diversity and abundance of breeding birds is obvious and inescapable.

Why don’t chipping sparrows breed in Florida?

Part of the reason for such divergent phenological trends in diversity between Florida and the rest of eastern North America derives from the incredibly high diversity of wintering birds here, of which I’m very appreciative. But it makes the dearth of birds during the breeding season so much more painful and sad. When they leave to repopulate the north, they aren’t replaced by tropical migrants coming in to take their place. What’s really puzzling to me is why so few of the species that winter here don’t establish breeding populations. There are so many species that are abundant breeders in the mid-Atlantic for which there appears to be suitable habitat for breeding, but for whatever reason, they don’t breed here. Take the ubiquitous winter visitor, the chipping sparrow. They are common breeders in Virginia in a variety of human-modified environments, many of which seem to be replicated in Florida, yet they don’t breed here. It’s something of a conundrum to me why so few sparrows breed in Florida – the specialized Bachman’s sparrow is the only breeding sparrow found in inland habitats in most of peninsular Florida (the critically endangered Florida grasshopper sparrow has a very limited range and is an extreme habitat specialist in the dry prairies of the southern half of the peninsula). In Virginia, it’s easy to find chippers, song sparrows, grasshopper sparrows, and field sparrows in a variety of successional or disturbed habitats during the breeding season. Why are there so few breeding species of sparrows in Florida?

Indigo buntings are common as dirt in agricultural or successional habitats in northern Virginia, but far less common as breeders in Florida.

Even for species with wide breeding ranges that do breed in Florida, like blue grosbeaks or indigo buntings, the difference in abundance between Florida and Virginia is striking. In mixed agricultural habitats, indigo buntings are as regular as telephone poles along some rural roads; it’s hard to find a spot in appropriate habitat where you can’t hear one singing somewhere. In Florida, indigo buntings aren’t terribly difficult to find as breeders, but in nothing like the densities seen further north.

This abundance map of indigo buntings during the breeding season was prepared from Breeding Bird Survey data by the U.S. Fish and Wildlife Service. The difference in abundance between most of the eastern half of the continent and Florida is huge.

For now, all I can do to deal with the loss of birds that’s underway is to learn to appreciate even more the hard-core birds that actually stay here to breed. And look forward to the first southward movement of migrating passerines, which will begin some time in July. That’s not that far away.

Epic battles

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April 15, 2014

While I was futzing around in the yard yesterday afternoon, replenishing the brush piles, I heard some rustling in the leaf litter and looked over to see a couple of Cuban brown anoles staring each other down. I don’t usually pay that much attention to the Cubans; they’re very feisty little beasts and all and that’s cool, but they’re so common it’s easy to take them for granted. Aside from the whole invasive exotic thing, they are amazingly watchable little lizards.

The face-off

Big daddy coming at you

What caught my attention about this pair was the spectacularly mottled color pattern of the larger male. I’m used to seeing the big males in a variety of earth tones from light grayish-brown to deep chocolate, often with some flecking or patterning, but subtle. This big guy I was watching was over the top. So I ran (not literally) inside and grabbed the camera, threw a macro on it, and rushed back outside, hoping the two combatants didn’t take it elsewhere. Needless worry – they hadn’t moved a micron from when I left a minute or two earlier. Like most reptiles, Cubans spend a lot of time not moving a muscle. But these guys weren’t relaxed – they were laser-focused on each other (and aware of me as well, but unperturbed as long as I didn’t move too quickly) and tensed to the max. Standing tall, saggital and dorsal crests erect, head elevated and cocked to one side. They were doing some pushups, but no dewlapping. They were ticking time bombs, ready to explode.

The charge

But they took their time to do it. For minutes at a time, they just faced off, with slight shifts in position, always mirrored by the other, until eventually the bigger guy made his move. Mouth agape, he charged and grabbed the slightly smaller male, and after a brief tussle tossed him aside. It was over almost instantly. When they crank it into burst mode, those little dudes can scoot.

Eventually they took their beef from the ground up into the brushpile. The dominant male was the first to climb a foot or so up a stick from the pile. He turned around, perched head downwards, and surveyed his domain. The lesser Cuban had heart, though. He climbed up the big guy’s branch looking for more. After a couple of bouts of gaping threats towards each other, they locked up again. The result was the same. Alpha dog tossed the subordinate off the brush pile. They apparently can generate a lot of force and velocity with those powerful necks. I’ve seen big males toss smaller lizards a foot or more.

There was no quit in this spunky male. He sported a regrown tail he probably lost in an earlier encounter with alpha.

The lock-up. The little guy is about to get the toss off.

Thoroughly entertaining. Cuban browns are not every Floridian’s favorite herp, but given that we’ve got them, why not appreciate them? In one of the labs I teach for an intro biology course for psychology majors I have students compare behavior of an ectotherm and an endotherm (cold-blooded vs. warm-blooded, if you must) to look for differences in activity level and behavioral complexity. The focal species are gray squirrels and Cuban brown anoles. I don’t even have to show the students how and where to find the lizards. They’re everywhere. I can’t imagine that there are many college campuses that have such an engaging herp in such abundance, easily observable most months of the year. In pedagogical jargon, they are a high-impact herp. And studying them is surely a best practice.

For anyone with an inordinate fondness for Anolis lizards, do yourself a favor and visit the blog of my friend and blogging inspiration Janson Jones. He raves with great regularity about the wonders of all things Anolis on his blog Dust Tracks on the Web. He does that far more eloquently than I can, for sure, but then he’s a humanities-type guy while I’m a blunt-edged scientist. It’s a stacked deck.

And don’t come back, you cheeky little bastard.

Darwin’s Goldfinches

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Two male American goldfinches molting into breeding (alternate) plumage

March 30, 2014

All real biologists love Charles Darwin, or Saint Chuck as he is sometimes known among the fraternity. Darwin’s genius was multifaceted; he was first and foremost a naturalist, and a damned fine one at that. In addition to his monumental bestsellers, The Origin of Species and The Descent of Man, Darwin wrote numerous books about more obscure biological topics, such as the sex lives of orchids, the role of earthworms in soil formation, and the emotional responses of humans and animals, among others. His fascination with the patterns of distribution and morphological diversity of the Galapagos finches (“Darwin’s finches”) is said to be one of the key observations that led him to his revolutionary evolutionary insights.

His greatest contribution to biology, though, was his elucidation of the principle of natural selection, and later, sexual selection. Darwin was certainly not the first scientist to suggest that organisms evolve and that one species can transmogrify over time into a new and radically different form. The Greek philosopher Anaximander is often credited as being the first to suggest that organisms evolve, way back in the 7th century BC. But Darwin (along with Alfred Russell Wallace, who tends to get lost in the mix), was the first to propose a credible and testable mechanism explaining how evolution and adaptation happen.

American goldfinches show tremendous sexual dimorphism (different appearance between males and females) during the breeding season, but not much during the winter. Males aren’t much brighter than this basic-plumage female.

Darwin’s principle of natural selection is surprisingly simple, and to those enchanted with biotic diversity and natural history, incredibly powerful as a tool for understanding. The process of natural selection is based on a few widely confirmed premises: a) individual organisms vary in many traits, b) variability among individuals in traits is heritable (i.e., traits have a partial genetic basis), and c) variability among individuals in these heritable traits results in differences in performance in the natural world. Most importantly, individual variability affects the ability of individuals to survive and ultimately reproduce. Those individuals who are more successful at reproduction will pass more of their genes to the next generation than individuals that reproduce less or not at all. Over the course of generations, the genetic composition of the organism will change. That’s evolution. The widely used term “survival of the fittest” does a very poor job of capsulizing the process. Natural selection is not so much about survival as it is about the ability to produce viable offspring carrying one’s genes, though successful reproduction does require that an individual survive until at least the age of reproductive maturity. Ultimately, though, difference among individuals in reproductive success, or Darwinian fitness, is the defining feature of Saint Chuck’s principle.

The mottled appearance of this male clearly shows old (basic) plumage being replaced by new (alternate) plumage. The black cap of males is only present in the alternate plumage.

Evidence for the basic premises of natural selection is overwhelming, and obvious to anyone who spends any time studying organisms and how they function in their real environment. Right now in Florida, evidence for one of those premises is obvious to anyone who maintains feeders that attract American goldfinches. Individual variability among goldfinches is on full display right now as they begin preparation for their northward migration and breeding season. It is a challenging task to find two birds that look exactly the same right now.

This male is in the early stages of pre-alternate molt.

Though individual variation in many traits exists in all bird species all the time, often it’s not apparent to dull-witted human observers, though I have no doubt it is obvious to the birds themselves. They know who they are. I absolutely adore the American crow family that visits my yard frequently, but except for the patriarch with a slight bill deformity (Longbeak, or LB), I can’t tell them apart, aside from the crude distinction between adults and younger birds that still show hints of brown in their plumage.

The slight difference in beaks between these crows is the only way I can tell them apart.

American goldfinches are undergoing their pre-alternate molt right now, and males are making the transition from their dull, female-like basic (winter) plumage to their alternate (breeding) plumage. Each male is on his own schedule, slightly or greatly out of sync with his mates. Some males have scarcely begun their pre-alternate molt, while others have nearly completed it. This in turn reflects tremendous variability in a panoply of physiological states correlated with the progression of molt, likely including serum testosterone levels in their blood. A rapid increase in serum testosterone levels in males during late winter and spring is a common phenomenon among birds breeding in temperate habitats; rising testosterone strongly influences a wide range of traits, including both plumage traits and reproductive behaviors like singing, male-male aggression, and in many species, territorial behavior.

A rare sight for me in Florida – a male that has nearly completed his pre-alternate molt

This male has nearly completed his molt, but not quite.

But why is individual variation in progression of molt so apparent in goldfinches, but not so much in other species? As it turns out, American goldfinches are unique in a number of aspects of their molting and reproductive behavior. They are the only species among their close relatives (cardueline finches) that undergoes a complete replacement of body feathers in the pre-alternate molt. Consequently, the magnitude of change between basic and alternate plumages of males is unusually large. The mottled appearance of many males, who have patches of new bright yellow contour feathers interspersed among the remaining duller basic plumage, makes each male slightly (or greatly) different from others.

Although American goldfinches don’t typically breed in central Florida, this alternate-plumage male appeared at my feeders, along with a female, in August of 2012, when goldfinches are usually still nesting. Interesting color variation in this male as well – he had no white feathers in the wings.

Asynchrony in the progression of molt among males is accentuated by their extended molting period, which can occur between March and July. At the time when most temperate passerines have finished breeding or are working on a second or third brood, American goldfinches are just getting ready to nest. They are one of the latest breeding species in eastern North America, with nesting activity mostly occurring in June through August. This may be related to their dietary specialization – they are among the most devoted seedeaters of any North American passerine. Many species that feed heavily on seeds during the winter, such as sparrows, switch to much greater reliance on insects when nesting, as animal prey provides more protein to the growing nestlings than seeds. American goldfinches, by contrast, feed their offspring primarily seeds, and in particular, they are addicted to the seeds of various species of thistle. Their relatively late breeding season may be an adaptation to the reproductive phenology of thistles – goldfinches don’t initiate breeding until thistles are blooming and setting seed. The young birds hatch at a time of maximum thistle seed abundance. This delayed breeding behavior may allow them to extend their pre-alternate molt over a longer period than most temperate passerines, allowing a much greater amount of asynchrony in molt than is seen in most other birds.

News flash – goldfinches love thistle seed. The Nyjer seed sometimes sold as “thistle” seed for feeders is not really a thistle, but another composite called Guizotia abyssinica. This is the Florida native Cirsium horridulum, an early-blooming thistle that will set seed and provide food for wintering goldfinches before they migrate.

Male American goldfinch feeding at heads of Cirsium nuttalii, a native thistle that blooms and sets seeds before the migrating goldfinches have departed.

In Central Florida, American goldfinches are relatively late migrants. I don’t usually see them until November. During the 7 years I did weekly bird censuses at Emeralda Marsh, I saw them in small numbers beginning in mid-November, but didn’t see large numbers until late January and February, when flocks of hundreds of birds could be found feeding on the elm fruits that were just maturing. Goldfinches are typically quite nomadic in the winter, traveling widely in search of their favored seeds. During most of the winter, I usually have no more than a half-dozen birds at my feeders, but in late March and April their numbers skyrocket. I have somewhere around 30-40 birds visiting my feeders right now. Perhaps some of this increase in numbers late in winter is due to depletion of natural seed crops.

Seasonal abundance of American goldfinches at Emeralda Marsh Conservation Area in Lake County, FL

So with all these birds around, massive individual variability in appearance, and physiology, of American goldfinches is apparent. What are the consequences of this variation in molt and appearance to the reproductive success (Darwinian fitness) of individuals? It seems like a safe assumption that differences in plumage characteristics are heritable, as they are in other birds whose genetics are well known. But is there a significant impact of differences in the timing of molt on the ability of males to obtain a mate and successfully reproduce? That’s a good question. Some evidence suggests that pair-bond formation may occur in pre-breeding flocks, so differences in plumage among males could be having their initial effects on reproductive success right now.

Keeping that plumage in peak condition requires a lot of maintenance. When the goldfinches aren’t devouring the seed in my feeders, they are usually roosting in a nearby oak, preening and loafing.

In American goldfinches, males winter, on average, further north than females, and precede them in their arrival at breeding habitats by about 2 weeks. Males that molt earlier may also migrate earlier, allowing them to claim the best breeding sites. In some other passerines, like American redstarts, research has shown that higher-quality males are the first to return to their breeding habitats, and they are able to stake out the highest quality territories. Does it work that way in American goldfinches as well, even with their delayed onset of breeding? Maybe. It bothers me a bit every year that I almost never see males that have fully completed their pre-nuptial molt; even the most brightly colored males usually have at least a few small patches of basic plumage remaining. Perhaps the males that have completed their molt are already winging their way north.

Male American redstarts that arrive first on breeding grounds are high-fitness individuals who get the best territories.

Plumage is looking good. He’s checking out his package to make sure all systems are go.

Making peace with the mockers

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One of the most elegantly beautiful of North American birds.

March 16, 2014

The arrivals of fall migrants and winter residents are the highlights of the birding year for me. Spring migration has its own feel and charm, but for numbers and diversity, it’s the southbound birds that give me more raw birding pleasure. So it’s always a good day when I get an FOS bird, even if it’s one that’s completely predictable in its time of arrival. But I get an even bigger kick out of the migrants that are not so foreseeable. Cedar waxwings are a prime example.

You know they are going to show up every year at some point, but exactly when, where, and in what numbers is never a given. Cedar waxwing abundance in a particular area can vary by an order of magnitude or more between years, in my experience.

Two winters ago was a big abundance year for waxwings in DeLand; in good years, there are sometimes flocks of hundreds to thousands of birds cruising around town for a couple of weeks in late winter. The appearance of the waxwings in town often coincides with the shift of American robins from their forest phase to their urban phase; waxwings and robins commonly flock together. One morning in February 2012 when I was driving to work I saw several flocks of a hundred or so birds around Stetson’s campus. As is typical of waxwings, they often don’t stay in one spot for very long, but I was ecstatic to find one large flock hanging around the Rinker Environmental Learning Center. Some of the birds were visiting puddles of water in the parking lot and on sidewalks, and others were flying down to the grassy lawn behind the RELC, apparently feeding on something , along with dozens of robins. It was a puzzling behavior, since waxwings feed largely on fruit in the winter, and there were no fruiting trees around that might have dropped fruits into the lawn. As it turns out, the waxwings were there to drink. The sessile, round leaves of the profuse pennywort in the less-than-well-manicured Stetson lawn were acting as collecting cups for water, and the waxwings were drinking from them.

Robins and waxwings were flocking together on the ground on this February morning. Strange.

Waxwings in flocks of dozens of birds were on the ground on this February morning. Strange.

Drinking from the cups formed by Hydrocotyle leaves.

Fresh water can be a highly sought after commodity.

I happened to have a camera with me that morning, and I was like a pig in shit for the half-hour or so I was able to photograph the waxwings. But I also had an 11:00 class to prepare for and I was getting antsy about that, so eventually I had to leave the waxwings and head to the office. I was able to process a few of the better photos before class and began that day with a mini-diatribe on the miracle of the nomadic waxwings, in the hope that at least one or two students might look for them in the next day or two. I don’t know if any ever did, but no doubt it was at least slightly more entertaining than the scheduled topic of the day. Cedar waxwings vs. Hensen’s nodes and dorsal lips of the blastopore – no contest.

Four years ago I planted a small dahoon holly (Ilex cassine) in one of my feeder gardens, hoping at some point, years down the road, to have a decent fruit crop and perhaps attract a feeding flock of waxwings to come and partake. Dahoon holly in the flatwoods of Tiger Bay seems to be one of the mainstays of winter frugivores; its berries seem to usually disappear long before some of the other less favored fruits, like winged sumac, or even American beautyberry. In addition to its bird-attracting properties, dahoon is just a lovely plant by itself, with a startlingly beautiful and apparent fruit crop in some years.

Dense fruiting display of a dahoon holly sapling at Tiger Bay State Forest. October 2012.

As it turned out, the cultivar of dahoon that I bought at my favorite nursery was not exactly like the wild dahoons I’m used to seeing in the flatwoods; the berries are smaller, the fruit color is more orangeish than scarlet, and the presentation of the fruit is less clumped and spectacular. Nonetheless, in the second year I had the dahoon, its meager fruit crop attracted waxwings to my yard on a morning I happened to be home, and I was able to get a few shots of the birds feeding. This year, the little sapling has had a tremendous growth spurt and is now 10-15 feet tall, with an impressive fruit crop. I was guardedly optimistic about photographing waxwings this winter.

Wild dahoon shown here is far more spectacular than the cultivar in my garden.

One of a couple of soft shots of waxwings at my little baby dahoon from last winter.

It’s been a low abundance waxwing winter here, though. I first saw or heard waxwings back in November, but as in most years, I didn’t start seeing them with regularity until February. But always small groups this year – I think the biggest flock I’ve seen has been 50 or so birds. Around my neighborhood, I’ve seen no more than a dozen at a time.

In the past week or so, on several occasions, I had seen groups of 2 to 5 waxwings hanging around the yard, and flying into the dahoon to feed. Their feeding forays on all of those occasions were aborted though, due to the aggressive behavior of my resident pair of northern mockingbirds, who have claimed the dahoon as part of their territory. They are pretty damned vigilant sentries; every time I’ve seen a waxwing in the area of the dahoon, a mockingbird has swooped in within a minute and driven the potential competitors away. It was starting to piss me off.

You have to admire the tenacity and take no prisoners attitude of Northern mockingbirds. Don’t you?

The mockingbirds harvest their fruit crop methodically; I’ve never seen one eat more than 3 or 4 fruits at a time. I suppose I should admire their planning and foresight, particularly compared to the gluttonous behavior of waxwings, who will sometimes completely strip a fruiting tree or shrub within hours of their initial attack. But I wanted photos of the waxwings, so the mockingbirds were not at the top of my list of favorite birds.

Yesterday, I heard several waxwings trilling and seeting from one of the wild cherries in my yard, and saw a couple more abandoned feeding sorties into the dahoon. I decided to exercise my very limited capacity for patience and set up on the dahoon and wait the waxwings out. I was also thinking that perhaps if I was somewhat apparent, it might have an inhibitory effect on the aggressiveness of the mockingbirds. Fat chance.

This waxwing was sticking to denser cover trying to avoid detection by the mockers.

I’ve rediscovered recently, probably for the 4^th or 5^th time since I’ve been doing photography, that if you want to get the most out of your optics, you have to use a tripod. I hate tripods. I had pretty much stopped using them entirely when I first started using lenses with internal vibration reduction (VR in Nikon lenses, OS in Sigma), but at some point a few months ago I tried some feeder shots with a tripod just for shits and giggles. The increased resolution and detail in the resulting photos left no doubt that as good as the vibration reduction systems are, handholding nearly always results in some image degradation under less than optimal conditions. So I set up the tripod, pointed the lens at the dahoon, and waited.

Persistence wins.

I got lucky. On several occasions in the next hour or two, groups of 3-4 waxwings came down to feed. I was particularly struck by how different their behavior was from what I’m used to. Flocks of feeding waxwings can be riotous with activity and noise, with birds constantly in motion, popping in to eat a few fruits and then flying off, to be replaced by other members of the flock. The waxwings yesterday were as silent as church mice, and fairly restrained and deliberate in their movements. They would stay in one spot and eat all the fruit within reach before a short hop or climb to a new fruiting spray. They were totally silent. Correlation doesn’t prove causation and all that rot, but I’m pretty sure the subdued behavior was due entirely to the terrorizing mockingbirds.

Trying to blend in with the trunk.

After the fifth or sixth time one of the mockers chased off a group of waxwings within seconds of them landing in the dahoon, my blood was boiling. How dare they? I tried a little playback of a variety of northern mockingbird vocalizations thinking that might distract them somewhat from the holly and allow the waxwings to sneak in and feed. No dice. They paid no attention to any form of playback. Based on that one piece of empirical evidence, I conclude that playback has no adverse effects on breeding passerines whatsoever. Insert sarcasm emoticon here.

But eventually I was able to photograph a couple of feeding forays, and the waxwings were still around when I had to leave around 4:30; in the end it was all good. My animosity for the mockers disappeared entirely. Well almost. They are pretty bad-ass little bullies sometimes, particularly towards birds smaller than them. That’s a behavior I have trouble getting behind. I think Atticus Finch was slightly underinformed when he told Scout that mockingbirds don’t do anything but make pretty music for us to listen to all day. They kick serious ass at times.

This morning brought a new perspective on the mockingbirds. Although there were several big clusters of fruit still on the dahoon yesterday when I left the waxwings, by 9:00 this morning it had been picked clean. The efforts of the mockingbirds to thwart the waxwings didn’t amount to much. The persistence and patience of the waxwings won the day. So my new and enlightened view of the mockingbirds is this: had they not kept the waxwings at bay for a couple of weeks, the dahoon would have been stripped bare long ago, probably at a time when I wasn’t around to see or shoot it. The mockingbirds were actually ackling for me in a way – they prolonged the presence of the waxwings long enough that I was ultimately able sneak a few shots. Thanks, NOMOs. I take back all that nasty shit I said about you.

No hard feelings, bud.

Lekking in DeLeon Springs

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March 8, 2014

To me, one of the most amazing achievements in field ornithology and bird photography of the last decade or two is the bird of paradise project, sponsored by the Cornell Laboratory of Ornithology. During the 8 years of this project, evolutionary ecologist Ed Scholes and biologist/photographer Tim Laman travelled 18 times to New Guinea, the center of diversity of these magnificent birds, to document and film the courtship behavior of all 39 species comprising the family Paradisaeidae. Ever since I obtained Cooper and Forshaw’s stunning 1977 masterpiece, The Birds of Paradise and Bower Birds, and spent hours poring over its oversized plates depicting their lavish colors and hypertrophied plumage, I’ve been in love with these birds. Outrageous sexual dimorphism and bizarre courtship behaviors, along with their exotic locale, made these birds seem otherworldly and alien to me. And they might as well be on another planet – I’ll never see one in the flesh. But I’ve seen something nearly as enchanting and mystical, in a residential neighborhood in lovely DeLeon Springs.

Tuesday morning began as most mornings this winter have. Despite forecasts of clearing skies and warming temperatures by mid-morning, it was a gray, cold, misty morning when John Serrao and I left for a birding cruise through Ocala National Forest. We had faint hopes that the warming temps might even produce a herp or two crossing the roads, but that was a fantasy. The dismal, dreary weather and dull light persisted throughout the morning. But we saw birds – lots of warblers and other wintering/migrant passerines were active, including some of the largest flocks of yellow-rumped warblers I’ve seen this season. As I’ve noticed on several other occasions over the last several weeks, many of the yellow-rumps were feeding on the ground, sometimes in the road, often along with palm warblers and chipping sparrows. Yellow-rumped warblers have one of the largest repertoires of feeding behaviors of any of the parulids; I wonder how this is related to their overwhelming abundance and wide range of habitats they use.

Yellow-rumped warblers are mainly foliage-gleaners, but will also feed on the ground, engage in flycatching, and feed on fruits and seeds at times

Despite the less than ideal weather, we actually managed to see a reasonable number of cool birds, including yellow-throated, orange-crowned, palm and pine warblers, ovenbirds, singing northern parulas, blue-headed vireos, hermit thrushes, ruby-crowned kinglets (occasionally displaying the full red crest to each other – just one more indication that testosterone levels are on the rise), Florida scrub jays, and so on. A thoroughly enjoyable morning, but mostly lacking in photo opportunities.

Despite the weather, singing northern parulas were one more bit of evidence that Spring is actually here.

Ruby-crowned kinglets are showing their red crests more often these days. They just won’t do it for me when a camera is aimed at them.

Most passerines were sticking close to cover and concentrating on feeding. This hermit thrush was a welcome exception.

As small, energy-limited passerines often do on cold or inclement days, most of the birds we saw were fixedly engaged in feeding. Maintaining or building up fat reserves seems to take precedence over most other activities on days like these. Response to pishing and playback was brief and minimal. We did lots of looking, relatively little shooting.

Scavenging bald eagle in the scrub

The best photo op we had in the forest was a nearly mature bald eagle feeding on roadkill raccoon on the shoulder of US19, along with a flock of black and turkey vultures. The eagle flew up into a lichen-covered oak skeleton as we approached, but gave us extended looks for several minutes, as cars and trucks zipped by.

Part of the DeLeon Springs peacock flock

The trip home produced our most memorable sighting of the day. There is a neighborhood in DeLeon Springs I often drive through when going to Woodruff or other locations north of DeLand that is home to one of the largest flocks of Indian peacocks I’ve seen. At times more than a dozen birds can be found in one small yard. That’s quite an impressive spectacle at any time of year. On Tuesday, we witnessed what is probably a common sight to those used to living with peacocks, but which I had never seen in its entirety – the full display of a peacock in peak breeding plumage. Absolutely mind-blowing. Charles Darwin once wrote that the “sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick!”, because he couldn’t fathom how natural selection could have produced such an overblown, seemingly useless adornment. It led him to develop his principle of sexual selection, hypothesizing that extravagant features such as the peacock’s tail have evolved in response to females’ preference to mate with males that have the most striking accoutrements. Evolutionary biologists have embraced Darwin’s principle of sexual selection, but still argue over the specifics of the mechanism. Why would females choose to mate preferentially with the most gaudy males?

Indian peacock (Pavo cristatus)

And what a gaudy display it is – I had seen males in low level display before, fanning the ocellus-adorned plumes of their tail feathers. I was surprised to learn that the prominent plumes with the startling ocelli (eyespots) are not true tail feathers (rectrices) at all – they are highly modified upper tail covert feathers, like the yellow feathers on the rump of a yellow-rumped warbler. But I had never seen the full display, which is prolonged, graded, and complex. It begins with a slight spreading and elevation of the train, but progresses to a towering display in which the train is held perpendicularly over the back. At its peak, the male quivers the train for several seconds in what seemed to me to be an almost orgasmic burst of pride. It reminded me a bit of this classic Saturday Night Live skit. As females walked by, paying no attention whatsoever to the displaying male, he slowly rotated to track their passage and show his erect train to best advantage.

The true tail feathers (rectrices) can be seen here behind the plumes, which are really upper tail coverts.

A moderate-intensity display.

A high-intensity display. The train is held perpendicularly over the back, and the male quivers the plumes for a second or two. The female ignored his efforts.

Not surprisingly, Indian peacocks have a polygynous breeding system, like many of the most spectacularly dimorphic birds or paradise. In these systems, males contribute nothing to reproduction other than their sperm. In the wild, females choose among several available males who display simultaneously in an arena-like location called a lek. In some lekking species, the male that occupies the central, preferred location in the lek obtains nearly all of the matings with sexually receptive females. Clearly, in such systems it is a great advantage to be a little gaudier than nearby males.

Full display.

Because males in these polygynous species have been freed of all parental duties and investments other than contributing a set of chromosomes (and centrioles), they often evolve spectacular plumages and displays to advertise the quality of their genes. That, presumably, is why females select the gaudiest males. Only males of superior genetic quality can afford to invest the time and energy in producing these extravagant displays, and by mating selectively with the showiest males, females ensure their offspring will be of high genetic quality. Further, their sons will inherit the genes for these high-quality displays, and are more likely to be successful as sires once they are mature.

What female could resist this gorgeous male? In fact, they all did. Maybe persistence is the key.

Anyway, that’s the way the system is supposed to work. Studies of mate selection by Indian peahens (the female of the species; only the male is a peacock) have produced mixed results. Some studies have shown that females do seem to prefer males with their full complement of ocelli over manipulated males whose ocelli have been selectively trimmed, but there also seems to be relatively little variation in the number of ocelli among unmanipulated male birds. There is no evidence that females prefer males with longer trains, even though train length is correlated with the diversity of MHC (major histocompatibility complex) genes in males. A seven-year study of peafowl in Japan showed that train characteristics played no part in female choice of mates, and further, that the extravagance of a male’s train was not correlated with other measures of his physical condition.

As is often the case, the reality of nature is more complex and perplexing than our simplistic models and hypotheses suggest.

Hunting ghosts

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Emeralda Marsh Conservation Area

February 23, 2014

The third weekend in February is a date I look forward to all winter long. That’s when the driving loop at Emeralda Marsh Conservation Area opens to traffic, and every year I return on that weekend, mostly to look for cool birds and whatnot, but also to relive many great memories of the thousands of hours I’ve spent there and pay homage to this lovely natural resource. It’s a pilgrimage of sorts.

For nearly seven years, beginning in January 2000, I visited Emeralda once a week to do bird censuses for the St. Johns River Water Management District. I made the 45-minute drive from DeLand to Lisbon, and back, nearly 350 times during those years. Looking back I’m still incredulous that I got paid to do something I loved so much. I half-expect one of Rick Scott’s goons to show up at my door any day to tell me the state wants its money back.

It’s hard to overestimate how much you can learn about seasonal changes in the natural history of an area simply by going back to the same place over and over again, at all times of year and in all conditions.

This blue-headed vireo was in a small mixed-species flock working the hammock at the entrance to the wildlife drive.

But that gig ended in October of 2006, and since then, I’ve been reduced to merely one more of the great unwashed who must wait for the 3-month window when the Water Management District opens the drive. I’m sure they have legitimate reasons for the restricted driving access to this rather large wetland, but it’s somewhat incredible to me that it isn’t open at other times of the year to the driving public, save for hunter access during duck season. Fall migration at Emeralda can be overwhelming. The huge numbers of yellow warblers that use the wetland edges in August and September during their passage through the state should be sufficient justification for opening it then as well.

Of course, the entire area is open to biking and hiking year-round, so only lazy malcontents like me, who aren’t willing to hump the several miles between the parking areas and the best birding spots, have reason to complain. So I do. In my defense, it’s hot as shit out there in August.

Female or juvenile northern harrier.

The ghost in reference is the male northern harrier, the so-called gray ghost. Every February I naively fantasize that this will be the year I finally get a photo op of these big, gorgeous raptors. Every year I’m disappointed. But not too much. I nearly always see at least one or two female or immature harriers, though getting close enough to photograph them well is a tall order in itself. For whatever reason, females and female-like immature birds, greatly outnumber males in every area I’ve ever seen them. I see dozens of harriers every winter, but only 1 or 2 adult males, if I’m lucky.

Northern harriers are somewhat unusual among raptors in that males are often polygynous, having up to five mates at a time. But that’s not due to unbalanced sex-ratios – at birth, sex ratios are apparently 1:1. Despite being philanderers, male harriers don’t rule the roost. Females are dominant to males, and prevail in nearly all aggressive encounters. Perhaps social interactions between the sexes force males into using slightly different habitats and from being as behaviorally conspicuous as the females.

Regardless, the hunt to photograph the gray ghost today was yet one more resounding failure, though I did see a couple of harriers at Emeralda. One of them was at a considerable distance in bad light, and I half-convinced myself it might have been a male.

Wild radish (Raphanus raphanistrum)

But the trip as a whole was anything but a failure. The wildlife drive at Emeralda Marsh is no Black Point; it can be pretty uneventful on slow days. But there is always something cool to see there, if your definition of cool is appropriately broad.

The drive to EMCA this morning was mostly in moderate to dense fog, but I was driving through gorgeous rural countryside along lightly traveled Lake County Road 42, which traces the southern boundary of Ocala National Forest for much of it’s length, so the drive was quite peaceful and relaxing. The ill-defined features of the surrounding habitat matched my state of mind – I had no clear idea or expectations of what I would find.

Palm warblers were abundant in both upland and wetland habitats throughout the morning.

As it turned out, though the fog cleared by 7:30 or so when I got to the northern end of the conservation area, it remained cloudy most of the morning. Cloudy, calm, with high humidity and mild temperatures. Perfect conditions for prolonged high levels of bird activity throughout the morning.

And spring was in evidence everywhere. Roadside vegetation, including forbs and woody plants, was exploding with new growth. Winter crucifers like wild radish and poor-man’s-pepper were blooming in profusion, willow catkins were in full anthesis and new foliage was appearing as well, and budburst was evident in many of the trees of the hammocks and swamps. There’s an old idea that’s been tossed around for years in avian ecology to try to explain the huge increase in breeding bird diversity of upland habitats in the northeastern U.S., compared to the southeast, and especially Florida. The idea is that the compressed growing seasons further north actually produce a much more intense burst of productivity in spring than do comparable habitats of southern climes, and that this huge burst of productivity supports a much higher diversity of higher-level consumers such as insectivorous birds. That may be true, but it’s hard to imagine a much greater burst of productivity than is going on in many Florida habitats right now.

Wild radish (Raphanus raphanistrum)

At the Yale-Griffin Canal, the first stop, the clucking of coots and chortling of moorhens all around was interrupted by the repeated shrill ki-ki-ki-ki of a northern flicker, a bird I didn’t see that often when I did censuses here. I even managed a few noisy, low-light photographs. A good start.

Are you freaking serious? That’s the best look you’re going to give me?

I briefly pulled into the large parking area at the exit of the wildlife drive, just a bit further south on Emeralda Island Road. A male northern cardinal was flying across the lot into the open hammock on the north, but was accompanied by a female that didn’t seem the right color for a cardinal. She landed on an open perch at the edge of the woods, and I was able to get bins on her for a moment before she disappeared into the brush. A female blue grosbeak. She uttered a few of her distinctive metallic pit calls from the thicket, clearly assuming I needed all the help I could get to make the identification.

Blue grosbeak

On to the wildlife drive proper. This 4+ mile loop transects a variety of habitats, including some lovely hammocks and successional patches, but mostly it passes through the impounded wetlands that make up the majority of this 7000+ acre piece of property.

Here I found all the ghosts I could ever want to encounter, but they were all friendly ghosts. Nearly every spot along the entire drive brings back a specific recollection or two of some memorable wildlife or natural history sighting. I could write a book. Wait, I did write a book. Nobody would publish it.

Common yellowthroats were beginning to sing a bit.

Who knows what I’ll remember about today’s trips and sightings a few years from now? Mostly I saw pretty run-of-the-mill stuff; lots of yellow-rumped and palm warblers, many foraging low in the vegetation, some beginning to show signs of breeding plumage; several blue-headed vireos and orange-crowned warblers, which I always get a thrill out of seeing, though neither is a particularly uncommon bird; FOS northern parulas, and several singing common yellowthroats; and so on. Nothing there to sustain a twitcher. But it’s all good.

FOS northern parula

Probably the highlight birds of the day for me were the swamp sparrows – they were everywhere. And in contrast to their typical skulky behavior, several birds gave me good, only partially obscured views. One bird even showed me a behavior I’d never seen in swamp sparrows (or any sparrow, actually) before – he was eating the just emerged buds and tiny leaflets of a willow tree. More and more in the last several years I’ve heard accounts of animals that clearly eat specific plant materials to self-medicate – maybe that’s the function of this bird’s behavior. Though sparrows are largely herbivorous during the non-breeding season, I’ve always thought of them more as primarily seedeaters, not folivores. Relatively few bird species are pure leaf-eaters; it’s just not a very nutrient-dense source of provender. Especially at the bud stage, it seems like the nutrient or energy value of these tiny leaves would be negligible. But maybe there’s something else in them of value to the sparrow. Willow extract has been used for thousands of years to treat fever, headache and inflammation. It’s the original source of salicylic acid, from which aspirin is derived.

Swamp sparrow eating willow buds.

Savannah sparrows are always abundant along the roadsides until they migrate north

Savannah sparrows are always abundant along the roadsides of the wildlife drive, until they migrate north

This limpkin was the best wading bird of the morning.

Emeralda Marsh Conservation Area is located about 5 miles west of Eustis, north of the small town of Lisbon. More information about birding Emeralda can be found at the 1960’s-vintage website here.

The Ultimate Ocala Loop

January 26, 2014

I’m always on the lookout for new birding loops. I do a lot of my birding by road-cruising. All other things being equal, I prefer to get out of the car and into the habitat. Unfortunately Florida habitats, like those in every other part of the world where I’ve birded, are not particularly welcoming to my people. So from a purely practical consideration, I can cover vastly more area and see more stuff by car than by my limited means of self-propulsion. Natural areas with extensive hard-packed trails are always a treat, but I’ve found that the more accessible a natural area is, the more heavily visited it is. Profound. I prefer my natural history outings to be populated mainly or entirely by folks I choose to be with. Which is often no one. Some might call me a misanthrope. I hate those people.

When birding by car, the ideal trip for me is a big circuit that satisfies several requirements: a) it involves little or no time driving on heavily traveled roads that are impractical for slowing, stopping or wildlife observation or photography, b) it includes as wide a variety of interesting habitats as possible, c) the good light for photography is on the driver’s side as much as possible, and d) it is centered on DeLand and can be completed in a half-day or so. Finding new loops that meet these criteria is always a big rush.

So armed with a sense of adventure and optimism, I tried a new loop yesterday, and I’m pleased to report that it is the ultimate driving loop for birding Ocala National Forest. That’s a pretty presumptuous claim given the hundreds of miles of drivable roads in Ocala, so I should probably qualify it by saying merely that it is the ultimate Ocala driving loop that I’ve experienced to date. Anyway, I was recently accused of being “full of crap” by one of the most accomplished blowhards and bullshitters I’ve ever known; if you buy the premise that nobody can spot a bullshitter like another bullshitter, then my credibility is pretty low to begin with. Making one more extravagant and insupportable claim probably won’t adversely affect whatever shred of credence I might have.

Paisley sunrise looking south towards Lake Akron

Paisley sunrise looking southeast towards Lake Akron

I left home about a half-hour before sunrise Saturday morning and drove west on 44 across the St. Johns River, heading for the southern edge of the forest, whose boundary is formed by State Road 42. I was hoping to hit Paisley just as the sun was rising; a big successional field slopes downwards towards Lake Akron just before you enter Paisley. When conditions are right, a big fog bank sometimes forms over the lake and creeps up slope across the field, producing at times a spectacular foreground for the rising sun. The clouds were pretty dense and gloomy on this day, though, and the sunrise was humdrum. Somber gray skies prevailed until mid-morning. From Paisley, I continued southwest on 42 through Altoona, arriving at Sunnyhill Restoration Area by about 7:45. There is a small tract of live oak hammock there that is lovely in its own right, drenched with epiphytes like Spanish moss and resurrection fern, but there were no birds active on this chilly gray morning. The pastures near the horse trailer parking lot produced a flock of killdeers calling and wheeling, and a barred owl called from a distant hammock, but mostly it seemed as if the birds were still waiting to begin their day.

Sunnyhill Restoration Area

I backtracked on 42 to SW 182^nd Avenue Road (Avenue Road ? Isn’t that a bit of overkill?) and headed north a few miles to FR14, and then north on FR 05 (labeled SE 205^th Ave and Nfr 579 on Google Earth). I first visited Forest Road 05 a few months back and was struck by the incredible diversity of habitats it traverses.

The predominant habitat along FR 05 is scrub, but that simple statement doesn’t begin to hint at the wide range of structural and floristic variants that scrub encompasses. From where I started at its intersection with FR14 on the south to its terminus where it intersects FR50 (Hopkin’s Prairie Rd) some fifteen miles north, FR 05 traverses pretty much every stage of the scrub successional cycle, from recently burned tracts containing nothing but charred trunks and a few scattered survivors to mature monoculture stands of old sand pine, ready to be burned or harvested. And everything in between. Throw in non-scrub habitats, such as the frequent ponds, wetlands and depressions that support different plant communities and the result is that while cruising FR05, you are rarely in the same habitat type for more than a mile or so. If that.

Words are inevitably inadequate to describe the charm of these scrub habitats. Perhaps images are more revealing.

Mixed scrub

A grassy piney depression that clear on what this habitat would be classified as.

A grassy piney depression amid the scrub. I’m not sure what this habitat would be classified as.

Gorgeous Grassy Prairie

An open savannah-like tract in the midst of the scrub

The desolation of recently burned scrub.

A couple of northern flickers were hanging around and doing the wicka-wicka pair-bonding display in one of the few remaining sand pines.

Regenerating early regeneration scrub, with mature sand pine scrub in the distance

Regenerating early stage oaky scrub, with mature sand pine scrub in the distance

For the first hour and a half on FR05, bird activity was still quite low. Cold, cloudy conditions often stimulate birds of forested habitats to stick close to dense cover; trying to find birds at the edges created by the forest roads can be pretty non-productive. Several big flocks (~100) of American robins flew over, but I only saw a few in the scrub. A couple of flocks of blue jays and an occasional house wren or cardinal pair were about all I could kick up at first. By 10, the cloud cover began to disperse, the sun blazed through, and the birds began to appear. The various forms of scrub can host big numbers of wintering passerines, including half a dozen or more species of warblers. In fairly short order, I was able to tick off pines, palms (a couple of westerns but mostly easterns), yellow-rumps, yellow-throateds, black-and-white, common yellowthroat, a distant ovenbird chewking repeatedly, and several orange-crowned warblers. Eight species of warblers within an hour or two in mid-winter? How are you going to beat that?

Yellow-throated warbler

Palm warbler, eastern race

Pine warbler, male

Pine warbler, 1st year

Black-and-white warbler

Blue-headed vireo

Orange-crowned warbler. I found these birds several times in different mixed species flocks.

As FR05 approaches it’s intersection with State Road 40, the main east-west artery through the forest, one can, if one likes, take a 3/4 mile jog to the southwest to the boat ramp on Half Moon Lake. Expert Florida naturalist and biologist Dr. Steve Christman tells me that he sees bears in this area all the time, but I saw none on this day. Lots of bear scat, though, along with that of other carnivores. In some areas of the forest, it seems there is a pile of scat in the road from bear, bobcat, coyote, raccoon, or some other mid- to large-sized mammal nearly every 50m or less. Which does hint at the answer to the age-old riddle – does a wild bear shit in the woods? Not all the time, apparently.

Cladonia lichens in a fringing hammock around Half Moon Lake

Taking the dead-end spur to Half Moon Lake will spoil the loopular purity of this route, though, so it shouldn’t be indulged in cavalierly.

Across State Road 40, FR05 continues north for another several miles, in the process dipping down to the elevation of and skirting the edge of lovely Zay Prairie. Just one of many grassland/seasonal wetlands that FR05 passes, but certainly the most fully visible from the road.

Zay Prairie

Just before FR05 ends where it intersects FR50, there is a network of trails in the Lake Eaton Sink area. A small parking lot marks the trailhead; it was here that I digitally photographed my first Florida scrub lizard (Sceloporus woodi) several months ago. No scelops out on this chilly day, but I noticed something else there for the first time. Signs with some of my photographs on them! Tres cool.

Red-shouldered hawk, prickly pear and common yellowthroat by the artist once known as Destructo

Red-shouldered hawk, prickly pear and common yellowthroat by the artist formerly known as Destructo

The turn to the east of the ultimate Ocala loop comes at FR50; I turned right there yesterday, but a turn to the left will take the non-loop fixated visitor to some lovely hammocks and wetland habitats surrounding Lake Eaton. And Lake Eaton itself is charming.

Mixed scrub along FR50

Forest Road 50 eventually takes you by one of the most gorgeous areas of the forest I’ve yet seen, Hopkin’s Prairie. And that’s a viable option for modifying the ultimate Ocala loop if you choose to do so. But I didn’t. I turned south on FR33 west of Hopkin’s Prairie, stayed on that well-traveled road for scarcely more than a mile, then turned east on FR46, which skirts the northern edge of magnificent Juniper Prairie Wilderness. If I had to pick one road for birding out of all the roads I’ve been on in the forest, it would probably be this one. It runs only about 5 miles from its intersection with FR33 to where it ends at State Road 19 just south of Silver Glen Springs, but the range of both scrub and sandhill habitats found in this relatively short stretch usually produces a wide diversity of cool birds. Including lots of Florida scrub jays. Last winter during the red-breasted nuthatch invasion, I found these endearing little scuts on several occasions in the mature sand pine scrub tracts along FR46. The vast landscapes of low-stature oaky scrub visible to the south of this road are awe-inspiring.

Red-breasted nuthatch from FR46 in November, 2012.

Wintering eastern towhee. Our breeding towhees have white eyes. Towhees are abundant in the oaky scrub of Juniper Prairie

At State Road 19, the slow-rolling, intense birding part of the loop ends and gives way to the high-speed, vista-scanning form of birding. I usually take 19 back to 40 and then work my way back to Deland from there, still passing through the vast Ocala National Forest along much of the route. But that only works if you live in Deland. For those of you non-DeLandites, feel free to modify the ultimate Ocala loop once it reaches SR19 as necessary to return to your place of origin or nearest convenient parallel dimension.

A snipe hunt in Ocala National Forest

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Title credit: E. Eugene Spears

January 12, 2014

Regenerating sandhills on FR11.

My buddies for life (I think) Skeate and Spears made their annual trek from the hellish cold of Banner Elk, North Carolina to pay me a visit this week. The three of us met as grad students in the fabled zoology department at UF back in the 80s, and they have been my closest friends since. All of us were Florida newbies, and we learned about community ecology and the terrestrial ecosystems of peninsular Florida from the same mentors at around the same time. Nonetheless, it was a major rush for me to spend a couple of days sharing my recently ignited passion for Ocala National Forest and its diversity of plant communities and landscapes with them by visiting a couple of my favorite spots in the forest. We had all taken Community Ecology at UF with field trips led by the great man, Dr. Archie Carr, whose knowledge and understanding of Florida natural history and ecology were nothing short of miraculous. So by comparison, my puny attempts to enlighten them somewhat about the scrub, high pine, and associated habitats were kind of laughable. But all we can do is take what we’re given, G. We had no particular target taxa in mind; we were just road-cruising, happy as scallops for whatever natural history nuggets we might chance upon.

In fact, this post might be better called the anti-snipe hunt, as it is antithetical in nearly every respect to the traditional snipe hunt. In a regular snipe hunt, a naïve nimrod is stationed somewhere in purportedly suitable habitat, preferably on a dark, moonless night, to wait for the mythical snipe to appear and bag it. It’s a very focused pursuit, but typically produces no useful outcome other than amusement for the instigators. By contrast, we were three unfocused but somewhat knowledgeable fellows, looking for nothing in particular, nearly constantly in motion, covering a lot of territory on a bright morning. And our efforts produced several useful outcomes, including crippling views of the legendary snipe. No capture other than digital, though.

Coachwhip

On Friday, we first visited a tract of private property a bit south of Astor Park that included the remains of some old sand-mining operation, and then we headed southwest towards the Alexander Spring section of the forest. As we tooled southeast on FR18 towards the 52 Landing boat ramp on Alexander Springs Creek, we saw (incredibly briefly) a 3-4’ snake speed across the road and into the cover along the margin. Perhaps as quickly as I’ve ever seen a snake cross a 20’ wide roadbed. I didn’t even get a look at the head before it disappeared out of sight, but the sand-colored caudal half of the body and rapid rate of transit was enough to identify it: coachwhip. As we savored the buzz of the sighting, we reminisced about the coachwhip we saw while on a Community Ecology field trip to the Ordway Preserve over 30 years ago. Most of the dozen or so grad students in the class, and a couple of faculty, were in the departmental van ahead of me. As I still am, I was a driving fool and so was following the van in my tortured old ’75 Ford Futura. I had to slam on the brakes and skid to a sudden stop in the sugar sand ruts as the van ahead of me did the same; the side door opened and about a half-dozen people exploded out of it in pursuit of the coachwhip that had crossed the two-track we were driving on through the successional pasture. Most of these herpetophiles were young men in their physical prime, but the great Dr. Carr, then somewhere in the neighborhood of 71 years old, beat them all to the beast and with a great flying leap pinned the coachwhip with his torso.

Coachwhip

The nasty masty turned around, clamped down on Dr. Carr’s nose, and held on. And Dr. Carr stayed chill, knowing that any movement might cause the snake to rake his not-insubstantial rows of sharp teeth through his rostral flesh. After a few seconds, the coachwhip, still mostly immobilized by Dr. Carr’s weight pressing on him, let go of his nose and looked around. One of the other members of the group immediately grabbed the snake a bit too far down the neck and pulled it from underneath Dr. Carr. The coachwhip promptly latched onto his hand and raked, causing him to begin gushing blood from numerous small lacerations. After they released the snake and it began its retreat from the band of stinking primates, I took two photographs of it as it periscoped and scanned its surroundings before boogying at top speed. When I received and viewed the processed slides, I saw that a small turkey oak seedling beside the snake was speckled with blood.

Skeate, Spears and Buckeye at Alexander Spring Creek.

Buckeye. This charming little canine played no significant role in any of the adventures related here, but he’s so damned handsome I had to include his portrait.

We had no comparable adventure with the Ocala coachwhip yesterday; it was gone before the three of us had even processed our sensory input and identified the snake as a coachwhip. Conclusion from this and countless other anecdotal evidence: Dr. Archie Fairly Carr Jr. was a great, great man.

Dr. Archie Carr, Jr. The most amazing man I've ever known personally.

Dr. Archie Carr, Jr. The most amazing man I’ve ever met.

The rest of Friday’s trip, which included Paisley Road and FR06, was lovely but unproductive of anything other than stunningly beautiful habitats. Our sampling of gorgeous and diverse habitats resumed on Saturday, when we took FR11 north from SR40, a bit west of Astor Park, and followed it to its end at Ocklawaha Lake, on the boundary of Ocala National Forest. Unlike most forest roads, the stretch of FR11 between SR40 and its intersection with SR 316 just northwest of Lake Kerr is paved. This section of FR11 passes mostly through scrub, though the range of scrub subtypes spans nearly the entire gamut, from recently harvested clearcuts to mature, even-aged stands of nearly pure sand pine, and all the intermediate successional stages connecting these two endpoints.

The first of the two black bears we saw on FR11.

Once north of 316, as FR 11 approaches the Riverside Island tract, the road reverts to the more typical yellow sand. It was here that within a stretch of no more than a mile or two we spotted two different black bears poking around the road margins. We stopped and glassed both animals for a minute or two from a distance of a couple hundred yards, and they glanced up the road at us but remained unconcerned until I tried to drive closer to them, at which point they both slowly retreated back into the sand pine scrub. It seems like there must be some meaning to the observation that in the 35 years I’ve lived in Florida, I’ve seen black bears in natural habitats (I’m not including the young bear I saw at 2 a.m. in the morning from about 5’ away destroying the bird feeder and pole just outside the window of my DeBary home, nor the one that wandered onto the Stetson campus one fall a few years back, climbed up into a smallish oak tree in front of the student union, and snoozed there for several hours as students and staff treated it like a rock star and gathered around to ooh and aah) maybe 11 times, and that eight of those sightings have been in the last 6 months. But more likely it is just a reflection of the random and unpredictable nature of actually seeing uncommon and wary wildlife.

Regenerating sandhills

Further north on FR11 the habitat transitions from scrub into regenerating sandhills, and then a bit further on, mature tracts of longleaf savannah where I had several killer encounters with roving clans of red-cockaded woodpeckers last year. The bright cloudy skies on this breezy morning provided the perfect diffuse lighting to accentuate the panoply of brown hues produced by the numerous conspicuous grasses. Luscious golden browns of Andropogon, creamy tans of wiregrass, a diverse range of intermediate tones from other grasses and senescent forbs – it’s a beautiful time of year to be in the sandhills.

Mature sandhills with wiregrass

At Rodman Dam, I was hoping for a variety of dabbling and diving ducks, but the only aquatic swimmers to be found were big flocks of American coots. While watching a couple of killdeer exploring the broad grassy berm of the dam, I saw a lone Wilson’s snipe toddling slowly up the slope. Confident that it would flush with a buzzy prrrrrt as soon as I got anywhere close to it, I idled towards it hoping to grab a shot or two. And behaving exactly like a consummately cryptic bird should, it surprised me by never flushing, ultimately allowing me to drive within about 15 feet and fire away to my heart’s content. It was still hunkered in the same spot as I slowly pulled away.

Wilson’s snipe.

The friends I made in graduate school were some of the finest people I’ve ever been privileged to know, and those relationships seem to sweeten and intensify with time like a fine wine. Can’t go back to those halcyon, treasured times, I know, but spending time with old friends like Skeate and Spears is maybe the next best thing.

Coco and her dude.

The post-script to this story concerns stuff we didn’t see. Before their visit, I was totally jazzed by the prospect of showing off the pair of painted buntings that had been visiting my gardens for the previous couple of weeks. But both those birds disappeared about a week before my friends arrived, and despite my repeated entreaties to the bird gods, the male never returned while they were here. Coco, the female, did put in brief appearances on Friday and Saturday afternoon, but the incomparably beautiful male waited until 3 hours or so after they pulled out this morning to make his return. The serendipity of natural history. Next year, my friends.

Graded signals

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Orange-crowned warbler.

December 28, 2013

A number of common Florida birds are named for features that are rarely seen. Ring-necked ducks, ruby-crowned kinglets, and bristle-thighed curlews come to mind. This morning I was relaxing on the patio, savoring my best Christmas present, Joe Hutto’s endearing Illumination in the Flatwoods: A Season With the Wild Turkey. I watched and listened as numerous flocks ranging from a few to several dozen American robins flew over regularly; it seems that they are beginning to shift to their urban phase. While totally mellowing on this gorgeous gray Florida day, I was fortunate to not only see, but also photograph a feature of one of these common Florida birds that I’ve seen only a few times. Ever. The orange crown of an orange-crowned warbler. (If you’re still scratching your head about the bristle-thighed curlew reference above, give yourself a pat on the back; it’s a joke. I’ve never seen one, in Florida, Hawaii, or elsewhere.)

Ruby-crowned kinglet, showing no sign of a ruby crown.

Ruby-crowned kinglet, showing not a hint of a ruby crown.

A low-intensity display of the ruby crown.

Many birds have plumage or structural features that serve as signals of some sort, and which can be widely variable in strength, or even their presence or absence. These graded signals allow nuance in communication between individuals. Exactly what is being communicated is often (usually?) hard to determine. Ruby-crowned kinglets have been tormenting me for years in my quest to photograph the full blown crest erection. Haven’t come close; a patch of red laid flat along the crown is the best I’ve been able to manage so far. I see ruby-crowns displaying their brilliant crest often enough that I have some intuition of its message – it seems to be an aggressive display towards conspecific males, and the degree of piloerection is an index of level of bad intent. Males will occasionally flare their crest in response to playback of ruby-crowned kinglet vocalization (though not while mobbing, suggesting it is a signal for conspecifics), and when interacting in chases and aggression with other males.

One of the more nondescript of Florida’s winter warblers, if it doesn’t show any prominent field marks like wing bars or head pattern, it could be an orange-crowned warbler.

In orange-crowned warblers, I’ve seen even a smidgen of the orange so few times that I have no idea when or how they deploy their display. A Google image search for orange-crowned warbler returns a ton of very nice images, but only a handful show any sign of the orange crown. And most of those are birds being held in the hand. My inference is that orange-crowned warblers never flare the crown to the degree sometimes seen in a highly agitated ruby-crowned kinglet, in which the red cap looks more like a mohawk than it does plumage.

Northern cardinal male with flattened crest. What signal is being sent, and to whom?

A more typical crest position.

Feather position alone can act as a graded display, with or without display of normally hidden color. The degree of elevation of the crest on a northern cardinal changes dramatically, occasionally disappearing entirely when an individual is alone and presumably totally mellowed out. For cardinals and blue jays, the erect crest is the default state. For many other “uncrested” birds, the flathead is the default state, and a prominent crest is displayed only briefly and infrequently. Think green heron here.

Chill green heron.

Mildly perturbed green heron.

Seriously pissed off green heron. Not surprisingly, it’s a teenager.

In other birds, the signal is always visible to some degree, but that degree varies tremendously. Male red-winged blackbirds sometimes throw me for a loop when I see them with their orange and yellow epaulets nearly totally concealed by other feathers. If I miss the sliver of yellow visible, I’ll begin to try and turn the bird into a more uncommon blackbird. At full display in a singing male, the epaulets are like brilliant orange-red flames.

Red-winged blackbird trying to conceal his true identity.

Full display.

Though I almost never see their orange crown, I see orange-crowned warblers fairly often, usually as single birds traveling with mixed-species winter flocks that can include titmice, chickadees, yellow-rumped warblers, kinglets, gnatcatchers, and small numbers of a half-dozen or more small passerines. I love mixed-species flocks. Orange-crowneds are one of the latest of the wintering warblers to migrate into Florida; while doing my Emeralda bird surveys, they usually didn’t appear until the third week of October or the first of November. Between then and their departure in late March (late entry, early exit), I saw on average 2-4 birds per census. Rather slow, deliberate leaf-gleaners for the most part, in low- to mid-level vegetation. They seem to like to investigate clumps of dead leaves. I once photographed one at Merritt Island NWR feeding on a large inflorescence of the flowering vine Mikania scandens; it was feeding on insects attracted to the flowers as well as on floral nectar. Orange-crowned warblers will puncture the base of some long-tubed flowers to gain access to the nectar. Seems like a very tropical behavior to me, though many of these birds will remain in the mild but temperate southeast for the winter.

Checking out the dead leaves.

Nectaring and gleaning at Mikania scandens

Feeding on nectar/pollen of willow.

Through most of the winter in Florida, the orange-crowned warbler is a very reliable bird, though I never see them in large numbers. I once saw a small flock of 4 traveling together in my backyard; they were leaf-bathing on a drizzly February afternoon in the wet foliage near the top of a big Senna bicapsularis. I saw a hint or two of the orange crown on that day as well.

Seasonal abundance at Emeralda Marsh Conservation Area, Lisbon FL.

Leaf bathing in Senna bicapsularis

The bathing orange-crowned today was taking the more formal soak and fluff in the birdbath, and I was able to watch him (only males have the orange crown, which probably says something about its function) for a couple of minutes. The orange crown was frequently visible, though it was probably coincidental to the normal feather fluffing and puffing that bathing birds do. There were no other orange-crowned warblers, or birds of any other species that I was aware of, nearby that this little guy might have been signaling to. Perhaps the relatively low population density of orange-crowned warblers accounts for some of the rarity of the display, especially when compared with the somewhat similar appearing ruby-crowned kinglets, which are typically much more abundant than orange-crowneds, and which often occur in larger numbers in mixed-species flocks.

I have to think even a highly enraged orange-crowned warbler’s display is still pretty subdued. The species account at Cornell’s Birds of North America Online has this brief tidbit (from Arthur Cleveland Bent’s monumental multivolume set of life histories of North American birds) about the orange crown display: “Male threat or alarm display can involve elevation of head feathers to display (barely) the orange crown patch (Bent 1953).” As graded displays go, the orange-crowned warbler’s is quite modest. So why does it give me such a thrill to see it?

Volusia Naturalist

A celebration of natural history

Category Archives: Blog

Why no sparrows?

May 10, 2014

Reference: Cook, R.E. 1969. Variation in Species Density of North American Birds. Systematic Biology 18 (1): 63-84.

The saddest season

April 27, 2014

Epic battles

April 15, 2014

Darwin’s Goldfinches

March 30, 2014

Making peace with the mockers

March 16, 2014

Lekking in DeLeon Springs

March 8, 2014

Hunting ghosts

February 23, 2014

The Ultimate Ocala Loop

January 26, 2014

A snipe hunt in Ocala National Forest

Title credit: E. Eugene Spears

Graded signals

December 28, 2013

May 10, 2014

Reference: Cook, R.E. 1969. Variation in Species Density of North American Birds. Systematic Biology 18 (1): 63-84.

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Title credit: E. Eugene Spears

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