Monthly Archives: October 2013

Black-and-white warbler

On playback and ethical bird photography

October 20, 2013

Most avid and responsible birders and bird photographers have two sometimes conflicting goals:  1) to see (and photograph) as many cool birds as possible, and 2) to minimize any harmful impacts that the pursuit of their goals might have on their subjects.

Although this gray catbird was attracted initially by mobbing call playback, he decided to have a bite while checking out the commotion.

Although this gray catbird was attracted initially by mobbing call playback, he decided to have a bite while checking out the commotion.

Among bird aficionados, there has been a long-running and sometimes acrimonious squabble over the impact of using recorded vocalizations (playback) to attract birds for viewing and photography.  I’ve been using playback in various forms for more decades than I’d really care to tally up.   Given that I consider myself an ethical birder, obviously I have strongly-held feelings about this issue.   The crux of the controversy is whether the use of playback to attract birds, for whatever reason, has any significant negative impact on the birds being attracted.  The standard argument against use of playback is that it might cause birds to expend limited time and energy resources responding to recordings, which in turn  could reduce their ability to deal with more pressing biological needs, such as feeding, finding a mate, or taking care of offspring.  Phrased from an evolutionary perspective, the question is does playback somehow reduce the fitness (lifetime reproductive success) of the birds that respond?  If so, it is a legitimate cause for concern, and perhaps even regulation and restriction of playback by birders.  Unfortunately, there is no hard empirical evidence that this is the case from any properly executed scientific study.  Both sides rely nearly exclusively on anecdote to make their case.

I used playback to entice this yellow-breasted chat into the open for photographs a couple of years ago. This bird gave me about 5 seconds of exposure before he lost interest and went back to what he had been doing.

I used territorial playback to entice this yellow-breasted chat into the open for photographs a couple of years ago. This bird gave me about 5 seconds of exposure before he lost interest and went back to what he had been doing.

The debate received an injection of hard evidence last week.  Three ornithologists published a peer-reviewed paper in the on-line journal PLOS One reporting the results of a rigorous study on two species of Ecuadorian birds (Rufous Antpittas, Grallaria rufula, and Plain-tailed Wrens, Thryothorus euophrys) and their short-term response to playback of species-specific vocalizations.   This study has been widely reported (and misreported) in the popular scientific press.  Here’s the main finding of the study extracted by the popular science writers at ScienceDaily, a respected and generally accurate website: the study “shows that playbacks do have potentially negative consequences, especially in terms of birds’ energies.”

Carolina wren, Thyothorus ludovicianus, a close relative of the Plain-tailed Wren studied in teh PLOS One paper. Carolina wrens are strong responders to mobbing and territorial playback; they are one of the "ringleader species" in many mobbing flocks.

Carolina wren, Thyothorus ludovicianus, a close relative of the Plain-tailed Wren studied in the PLOS One paper. Carolina wrens are strong responders to mobbing and territorial playback; they are one of the “ringleader species” in many mobbing flocks.

The problem I have with reporting this as a major finding of the study is that it just ain’t so.  The data reported in the study provide no evidence whatsoever for negative impacts of playback on these two tropical bird species.  There are no data presented here (or anywhere, as far as I know) dealing with the energetics (and their adverse consequences) of response to playback.   That is pure, unadulterated speculation, without even ancillary evidence presented to support such extrapolation.

Do birds have to abandon other necessary activities to respond to playback? Not this titmouse, who snagged a big juicy puss-moth caterpillar (Megalopyge sp.) while looking for the predator that wasn't there.

Do birds have to abandon other necessary activities to respond to playback? Not this titmouse, who snagged a big juicy puss-moth caterpillar (Megalopyge sp.) while looking for the predator that wasn’t there.

What the Ecuadorian study did show, quite convincingly, is that these two bird species are attracted by playback, and they alter their vocal behavior by singing and calling more frequently after playback.  Well, that’s a real shocking conclusion.  Birds do respond to playback.  Who knew?  Only millions of researchers, birders, and bird photographers who have used playback since recording and playback equipment made such manipulation of bird behavior possible.   It’s why we do it.   However, the PLOS One study provides no data WHATSOEVER that this change in behavior has any adverse consequences to the birds.  In fact, what their data show for the wrens is that repeated playback to the same birds over a 12-day period resulted in a precipitous decline in response.  In behavioral jargon, the birds habituated to the stimulus and pretty much stopped responding to playback entirely.   They learned.   Birds, as it turns out, are quite good at learning.  In the authors’ own words in their last paragraph, they state “This result suggests that playback could negatively affect species if they become stressed, expend energy, or take time away from other activities to respond to playback.  By contrast, the habituation results we present suggest that frequent birdwatchers’ playback may have minimal impacts on wren behavior”.

An ovenbird lured to an open perch by mobbing call playback. This bird doesn't look stressed or frightened to me - it is intensely curious. I think he's digging the moment.

An ovenbird lured to an open perch by mobbing call playback. This bird doesn’t look stressed or frightened to me – it is intensely curious. I think he’s digging the moment.

In other words, their study doesn’t really allow any conclusions at all about the long-term effects of playback on these species, but what data they do have actually support the idea that it’s negligible.  To conduct such a study looking for a long-term effect of exposure to playback and document any effects it might have on mating success or overall reproductive fitness is an order of magnitude or two more difficult than documenting a short-term response to playback.  More studies like the PLOS One study need to be done, but let’s not kid ourselves that they really tell us anything meaningful about long-term impacts.  They show that birds do respond to playback.  No Nobel Prize to be had for quantifying that, though.

In fact, one pair of wrens in the study built a nest 10’ away from the playback speaker.   As anecdotal evidence goes, that’s a pretty strong piece of information supporting the minimal impact interpretation. Other published studies on other species have even suggested a positive effect in some cases.   A study of Black-capped Vireos, a rare, local, and highly-sought species by birders, showed that repeated playback of vireo song in an area actually attracted more vireos to that site, and some of these birds nested in the area to which they were attracted and increased the local population.   Negative impacts of playback?  I’m not seeing it.  Which is not to say that it can’t or doesn’t occur; there simply isn’t any hard scientific evidence to support it.

The Lake George summer tanager on my first visit in April.

The Lake George summer tanager on my first visit in April. This is the tanager who graced me with his very near presence and a brief conversation. If only I knew what he really meant by “pituck”.

But anecdotal evidence?  Everybody has anecdotal evidence.  I’ll share some of mine.  On April 14 of this year I found a territorial male summer tanager in Lake George State Forest, and he responded strongly to playback by close approach  and  repeated flyovers to and from nearby perches.  Not all individuals respond this strongly; my wild-ass guess across species is that maybe only one out of every 5-10 territorial males to which I broadcast recorded vocalizations actually responds by approaching and singing back.  Most often I use playback from my car, which acts as a blind of sorts as long as I minimize any sudden movements.  This particular male actually landed on the window of my car, perhaps a foot away from my head, perched there for about 5 seconds, looked me straight in the eye and said “pituck”.  He then turned and flew back to a nearby perch.  It blew my freaking mind.  I was in a state of extreme elation for the next hour or two.  Being that close to a wild bird who is that close to me of its own volition is an intense and exhilarating experience, which I’ve experienced on a few other occasions when using playback.  How was it for the bird?   As I slowly drove away, I saw and heard him resume his circuit of singing perches he had been using before I began playback.  For all I know, that bird was, in his own mind, one bad-ass mofo.  He had confronted and repelled a bizarre and gigantic territorial interloper.

On my second encounter with this male, not only did he have a female following him, but he also caught several insects while he was responding to playback.

On my second encounter with this male, not only did he have a female following him, but he also caught several insects while he was responding to playback.

Fast forward to June 23, when I returned to that location with my buddy John Serrao.  John was jazzed about the idea of seeing and photographing a male summer tanager at close range.  I was a bit dubious about the likelihood of a strong response; it was much later in the nesting season, and in my experience, the most intense responses to territorial song occur early in the nesting cycle when the males have just established territory and are seeking a mate, and are intent on keeping other scumbag males away from their mate.  Nonetheless, when we heard a male summer tanager singing in the area (almost certainly the same bird I’d worked over a month earlier), we tried playback.  BAM.  He was all over us like stupid on a Tea Partier.  With one important distinction – this time he was being followed around by a female who seemed to be supporting his territorial defense.   As I did earlier, we worked that bird for perhaps 5-10 minutes and left.  Once again he resumed patrol of his territory and his habitual song perches as we drove away.

Summer tanager female who responded with her mate on my second encounter.

Summer tanager female who responded with her mate on my second encounter.

My conclusion from these encounters?  The earlier bout of playback had no effect on the ability of this male to defend his territory and obtain a mate.  Some research has shown that playback to territorial males can increase their serum testosterone levels, which typically show a huge spike during the breeding season for many male birds.  In all likelihood, that results in an increase in the perceived dominance status of that particular bird, and may actually increase their ability to defend a territory and attract a mate.   Egregious speculation?  Maybe.  But that seems to be the standard of evidence in the debate over playback and the ethics of using it to attract birds.

Here’s another side of the playback debate that’s rarely (like never) addressed: there is more than one type of playback, and more than one type of response.  Conclusions drawn from studies on one class of playback response are probably completely inapplicable to other categories of response.

The category of playback most opponents focus on is species-specific playback of territorial song to breeding birds.  Male birds of some territorial species (but by no means all) do respond strongly to such playback, and in some instances, an individual bird will continue to respond over a prolonged period (hours? Again, no empirical studies that I know of).   If an individual male is repeatedly subjected to territorial playback, it’s not hard to imagine that other critical activities of that male might be reduced due to overstimulation.  I’d like to think that anyone using playback would do so with some modicum of restraint and common sense, but I know there are jackass birders, just as there are dillweeds in every other human pursuit.

House wrens seem to have a rollicking good time while scolding a potential predator.

House wrens seem to have a rollicking good time while scolding a potential predator.

I restrict playback of territorial song to any individual male to no more than 10 minutes, and don’t work that bird again for at least several weeks.  In the vast majority of playback episodes I perform, it is a one-shot deal for that particular bird.  I never use playback in heavily visited areas or when other birders are nearby.  I do almost all of my birding and photography in sites that are not birding hotspots.  Often I see only a handful of other people on any particular birding trip, and most of those people usually aren’t birders.  Obviously, birders visiting heavily-visited areas or seeking to find well-publicized rare birds should exercise a high level of restraint in the use of playback.  But they don’t always do so.  News flash:  some people are dicks, be they birders or not.

The other distinct category of playback, which I use far more frequently, is the use of owl calls (screech owl quavers in particular) and alarm calls, scolds, buzzes and chips that are used by birds engaged in an amazing behavior called mobbing.  While territorial playback is generally restricted to a fairly short window of time during the breeding season, elicited mobbing responses can occur throughout the year.

Many birds respond poorly or not at all to playback most of the time. No playback was used in making this shot of a bald eagle at sunrise/moonset.

Many birds respond poorly or not at all to playback most of the time. No playback was used in making this shot of a bald eagle at sunrise/moonset.

And the behavior is a completely different beast than territorial behavior.  Mobbing is a contagious, multi-species affair – the more the merrier.  The strongest responses are evoked from mixed-species flocks containing a half-dozen or more species, often including titmice, chickadees, wrens, warblers, vireos, and a wide variety of other passerines (and some non-passerines, including woodpeckers and hummingbirds – hummingbirds are particularly fearless when responding to mobbing playback).  These birds will travel hundreds of yards (sometimes) to seek out the apparent predator, for reasons and benefits that are not well understood (and certainly not empirically quantified).  While engaged in mobbing behavior, these birds are vocal, active and highly excited.

Is responding to mobbing playback harmful to birds?  No studies address this point at all.  From a methodological and logistical perspective, that would be a very difficult study to carry out.  But I think it’s unlikely to have any significant effects.

Blue-gray gnatcatchers are among the most enthusiastic mobbers. Little dudes have no fear. I had one fly into my car once while looking for a predator.

Blue-gray gnatcatchers are among the most enthusiastic mobbers. Little dudes have no fear. I had one fly into my car once while looking for a predator.

Mobbing response to playback is an extremely transient behavior.  When the birds do respond (and often they don’t), they sometimes approach quickly and engage in frenetic activity and vocalizations for a few minutes. After 5-10 minutes of seeking and failing to find the predator, they shut it down and leave, returning to what they were doing before.  You can’t re-attract those birds by mobbing playback, at least in the short term.  It seems to be a very rapidly-occurring form of habituation, which then shuts off the response for some undetermined period of time.  The nature of the behavior itself limits its potential impact on the individuals that respond.

Cold, rainy conditions severely suppress mobbing behavior. Birds only mob when their other more immediate biological needs are taken care of.

Cold, rainy conditions severely suppress mobbing behavior. Birds only mob when their other more immediate biological needs are taken care of.

And often they don’t respond.  Cold, windy conditions tend to suppress mobbing response almost entirely.  During the breeding season, when mobbing species are defending territory and taking care of mates and offspring, it’s hard to elicit any response at all.  There is huge variability, both seasonally and on a shorter-term basis, to the strength of response.  My interpretation of this variability is that mobbing is a low-priority behavior, with little immediate benefit, that is frequently abandoned when other biological needs (feeding, territorial defense, breeding activities) take precedence.

Am I “stressing” these birds out by attracting them with mobbing playback?  I’d argue emphatically that I’m not.  Even superficial observation of the behavior of mobbing birds tells me that they aren’t frightened by the predator or otherwise stressed out.  In contrast, my HIGHLY subjective interpretation of the behavior of mobbing birds is this:  they love that shit.  I think it’s an exciting, rewarding behavior for the birds that do it, and it provides some internal neurochemical reinforcement making it a highly enjoyable activity.   I think it’s something like an adrenaline rush for these birds.  Sometimes I can almost hear what they are vocalizing in a Dr. Dolittle-type fashion: “Oh boy oh boy, we’re going to kick some predators’ ass!”.  How’s that for egregious speculation?

Playback works poorly for attracting snakes. No ears.

Playback works poorly for attracting snakes. No ears.

One last point about the use of playback: as an educator, I can’t imagine teaching my Ornithology classes without using playback to enhance the birding experience of the students.  Earlier this week while on one of our biweekly field trips, I placed the speaker and Ipod (with several custom-made mobbing vocalization tracks installed) at the base of a clump of winged sumac, and for the next five-ten minutes, the students and I were treated to a progression of very cool birds that came down to check out the jam.   We got crippling looks at cardinals, Carolina and house wrens, a pine warbler, a common yellowthroat, gray catbirds, and a couple of white-eyed vireos, all of which perched briefly in the open as they scoured the sumac, while the class enjoyed the antics of these birds from 15’ away.  When they began to drift away, as they ALWAYS do within 10 minutes or so, I turned off the mobbing track and all those birds resumed their prior activities.  No harm, no foul.  But a handful of budding bird-lovers got looks at those birds that they would never get otherwise.

Obtaining good unobstructed views of skulky birds like this white-eyed vireo can be very difficult without playback, particularly for a group of inexperienced birders.

Obtaining good unobstructed views of skulky birds like this white-eyed vireo can be very difficult without playback, particularly for a group of inexperienced birders.

Did we alter the birds’ behavior by eliciting a mobbing response?  No doubt we did.  Was it harmful?  Hard for me to envision how.  The birds wouldn’t have responded if they had other more critical needs to attend to.   Birders alter the behavior of their subjects all the time.  They frequently cause birds to retreat to cover just by their presence.   Most birders that I have known use the technique called “pishing” or “squeaking” to attract birds or draw them out of cover.  These techniques involve making shushing noises or other sounds that mimic the mobbing calls used by a wide variety of birds to provoke a mobbing response, or at least an investigatory response, by the birds they would like to see better.  They elicit exactly the same response that is provoked by playback of recorded owl vocalizations or mobbing calls using electronic playback.  Any birder who uses pishing but who is also opposed to the use of screech owl/mobbing playback to attract birds is a hypocrite.

Many (most?) birders use pishing or squeaking noises, which imitate mobbing or alarm calls, to get shy or secretive birds like this sedge wren to pop up and take a quick looksee.

Many (most?) birders use pishing or squeaking noises, which imitate mobbing or alarm calls, to get shy or secretive birds like this sedge wren to pop up and take a quick looksee.

Here’s an anecdotal and apocryphal birding tale (urban legend?) I’ve heard many times over the years regarding the impact of hard-core birders on their quarry.   As the story goes, a guided group of birders was visiting some marsh habitat in the northeast in search of the secretive and rare black rail, which had previously been reported from this site.  They assembled at the field site before dawn, and blindly trudged through the muck of the marsh in the dark to get to the site where the rail had last been seen. As the morning light came up after a period of unsuccessful listening for the bird, someone finally spotted it.  Trampled to death in the mud by members of the birding party.  True story?  Probably not.  But it emphasizes the point that we modify nature and alter the behavior, and perhaps sometimes the fitness, of our subjects nearly every time we go into the field.  All we can do is try to be aware of the potential harms, and try to minimize our impact.

Use of playback can sometimes have dire consequences. This northern parula was so excited at the prospect of kicking some predator's ass that he twisted his own head clean off. It was a sad sight to see.

Use of playback can sometimes have dire consequences. This northern parula was so excited at the prospect of kicking some predator’s ass that he twisted his own head clean off. It was a sad sight to see.

Bottom line: is playback harmful?   It COULD be, under specific conditions, although we don’t really have any hard evidence about what exactly those conditions are.   It’s pretty easy, however, for ethical, knowledgeable birders to anticipate many of those conditions and avoid them.  Personally, I have no qualms at all about using playback in the way I do.  I sleep like a baby after a day in the field of playback.

P glauc Limeniti_10112013-00_Heart Island N

Color pattern conundrums

October 13, 2013

I had tempered hopes for finding new and interesting migrants when I left home before sunrise Friday morning.   Fall break, a whopping two days, allowed me to forget about classes and go anywhere I desired.

I do most of my birding and natural historizing inland, at sites relatively close to DeLand.   Coastal sites, both on the Atlantic and Gulf coasts, routinely produce higher diversity and abundance of neotropical migrants than do inland sites, but I always feel a little guilty burning gas for longer road trips when cool stuff is surely nearby.   The superiority of coastal sites isn’t surprising given that many of the migrants I’m most interested in follow migratory paths that take them out over open ocean or gulf, and come to land when forced down by storm fronts or local weather systems that  forestall their long-range movements.  So they tend to concentrate along the coasts until conditions improve, during which time they can replenish their fat reserves for the long flight to come.  If conditions are good, many migrants bypass Florida entirely en route to the tropics.

Female American redstart.  Tomoka State Park

Female American redstart. Tomoka State Park

Tomoka  State Park was my primary destination, where veteran bird-bander Meret Wilson had reported some great birds in the preceding week (including a Swainson’s warbler, which would be a lifer for me).   I had misgivings though, as Friday morning followed two nights in a row of clear skies, which tend to favor departure of migrants that have been delayed along the coast.  That apparently was the case on this Friday morning, as Tomoka was mostly devoid of anything other than resident species like northern cardinals and Carolina wrens.  One small flock that included an American redstart, a yellow-throated warbler and a couple of prairie warblers contained the only migrant passerines I found there.

Balduina angustifolia, or Coastalplain Honeycombhead.  Heart Island Conservation Area

Balduina angustifolia, or Coastalplain Honeycombhead. Heart Island Conservation Area

Palafoxia integrifolia, or Coastalplain Palafox. Heart Island Conservation Area

Palafoxia integrifolia, or Coastalplain Palafox. Heart Island Conservation Area

The great thing about natural history and biotic diversity, though, is that there is always something cool going on somewhere.  So mid-morning found me back inland, at Heart Island Conservation Area.  This was the SR11 entrance to Heart Island, just a bit north of the intersection of SR40 and SR11.  The mostly flatwood habitats there were full of fall composites attracting a diversity of nectaring butterflies.  The flora included several of the purple-flowered species, including  Carphephorus corymbosum, a couple of species of blazing star (Liatris spp.), big gorgeous patches of Balduina angustifolia, and a species of Palafoxia I hadn’t seen before.  The biggest attractor for butterflies on Friday morning were the big white-topped asters (Sericocarpus tortifolius;  thanks, CB), some of which produced flowering spikes over six feet tall.  They were buzzing with activity from both butterflies and bees.

Palamedes swallowtail (Papilio palamedes) at Carphephorus corymbosum.  Heart Island Conservation Area

Palamedes swallowtail (Papilio palamedes) at Carphephorus corymbosum. Heart Island Conservation Area

Grass skipper (species undetermined) at Balduina angustifolia.  Heart Island Conservation Area

Grass skipper (species undetermined) at Balduina angustifolia. Heart Island Conservation Area

Butterflies visiting these big composites spanned a huge range in size, from small drab orange skippers to gargantuan tiger swallowtails.   There were also several viceroys at one of the clusters, indicating that there were willows nearby.   Viceroy larvae feed mainly on willows, and the adults don’t seem to wander far from the vicinity of their larval foodplants.   The most exciting lep, to me, nectaring  at the Sericocarpus was a single great purple hairstreak (Atlides halesus), a species that I just photographed for the first time a couple of months earlier.   Hairstreaks are among the smallest of the butterflies, but great purples are giants amongst their confamilials.   And this one was not only in pristine condition, but was very deliberate in his foraging movements, repeatedly visiting the same flower clusters and working slowly from one disc flower to the next.  I spent more than a half-hour tracking this one individual, waiting for him to move close enough to me and position himself appropriately for photos.

Tiger swallowtail female at Sericocarpus.  Females have extensive blue on the hindwing, lacking males.  Heart Island Conservation Area

Tiger swallowtail female at Sericocarpus. Females have extensive blue on the hindwing, lacking in males. Heart Island Conservation Area

While watching and waiting for this one butterfly, I found myself wondering about his spectacular color patterns, and what functions they might serve.  How had natural selection favored the evolution of such a delicate piece of living jewelry?

Great purple hairstreak at Sericocarpus

Great purple hairstreak at Sericocarpus

Brilliant colors and striking contrast are two of the components of pattern in both butterflies and birds that attract so much attention and admiration from naturalists, yet it struck me that we understand relatively little about how these patterns are actually adaptive, beyond a few simple generalizations.

Hairstreaks, for example, are usually instantly recognizable by the adornments of the hindwings.  Most have a pair of thin tendrils extending from the back of the hindwing, and the hindwing is often marked on the underside with spots of color that look something like eyes.  When perched, most hairstreaks habitually rub their hindwings back and forth across each other slowly, while movements by the rest of the insect are slight and barely noticeable.  The adaptive function of the tendrils, spots and movement seem to be to mimic a head and antennae, which presumably misleads potential predators into directing their attack to the hindwings.  It’s not uncommon to see hairstreaks with symmetrical chunks removed from both hindwings, indicating that a predator wannabe fell for the ruse and got nothing but a mouth or beak full of chitin and scales.  The hairstreak survives the attack only a little the worse for the encounter.

This gray hairstreak shows apparent predator damage to the rear of its hindwings.

This gray hairstreak shows apparent predator damage to the rear of its hindwings, suggesting that the tendrils and eyespots there enticed the predator away from the head.

So I get that part.  But what about the other pattern components that are so conspicuous, such as the patches of lime-green scales on the hindwings, and the brightly bicolored orange-blue abdomen?   As much as I love all things Gator-related, that seems unlikely, although there are also some very cryptic grasshoppers that have brilliant contrasting orange and blue patches on the inside of their hindlegs, visible only briefly and sporadically, that must have some kind of signaling function.  Why orange and blue?

Great purple hairstreak. Heart Island Conservation Area

Great purple hairstreak. Heart Island Conservation Area

And then there’s the southern aspect of a great purple hairstreak traveling north.  Not only do they have the wispy tendrils and eyespots on the hindwings – they also have flanges extending from the rear margin of the wings that produce a remarkably face-like visage as the butterfly is walking away.  What is that supposed to look like?  I’m hard-pressed to ascribe a resemblance to any insect I can think of, but it seems likely to me that this is also a feature favored by natural selection somehow, perhaps because of some protective function.

Great purple hairstreak from behind.  Heart Island Conservation Area

Great purple hairstreak from behind.  What kind of face do you see?  Heart Island Conservation Area

The swallowtails represent an entirely different suite of characteristics, but are similar in some respects to the hairstreaks.  Big, conspicuous, almost constantly in motion, brightly colored – the overall effect of the swallowtail motif can’t be concealment.   A couple of the tiger stripes, however, converge towards the abdomen, and in many swallowtails there are conspicuously colored spots just below the convergence of these stripes that could function as eyespot mimics.   The tails of swallowtails may serve a similar function to the tendrils of hairstreaks, attracting the attention of predators towards these disposable and dispensable wing pieces.

Male tiger swallowtail at Sericocarpus.  Heart Island Conservation Area

Male tiger swallowtail at Sericocarpus. Heart Island Conservation Area

One big difficulty in interpreting color patterns and their functional significance lies in the realization that human observers often aren’t even seeing the color patterns other butterflies, or their predators such as birds, might be seeing.  Many insects and some birds can see well into the ultraviolet range of the color spectrum, invisible to humans.    Butterfly wings (and flowers as well) reflect heavily in the UV, so what appears to be a single color without any obvious pattern to us is richly patterned to a potential predator, conspecific, or nectarivore.

Viceroy at Sericocarpus.  Heart Island Conservation Area

Viceroy at Sericocarpus. Heart Island Conservation Area

Even in species where we think we have a clear understanding of the significance and evolutionary logic behind butterfly color patterns, the full story is sometimes more complex than initially imagined.  Take Viceroys, which traditionally have been considered to be a classic (Batesian) mimic of the unrelated monarch butterfly.  Any decent naturalist can tell a monarch from a viceroy pretty easily; not only are there differences in specifics of the color pattern (especially a transverse black band on the upper hindwing of viceroys, lacking in monarchs), but also major differences in flight patterns.  Still, as the old story goes, viceroys gain protection from predators because of their similarity to monarchs (and other danaids like queen butterflies).    Monarchs are avoided by many predators because they feed on and store (sequester) toxic compounds from their larval hostplants, which include various species of milkweeds (Asclepias spp) and relatives (such as Sarcostemma).   These compounds, called cardenolides, cause fairly immediate digestive upset in naïve predators that try to eat one, and they quickly learn to avoid any similar appearing butterflies in future feeding attempts.  Monarchs have evolved a bright and conspicuous orange and black color pattern to warn potential predators of their toxicity. This pattern of warning coloration is known as aposematic coloration.

Monarch (Danaus plexippus).  In the traditional explanation, the monarch is the model (unpalatable species) for the viceroy (palatable species) in a Batesian mimicry system

Monarch (Danaus plexippus). In the traditional explanation, the monarch is the model (unpalatable species) for the viceroy (palatable species) in a Batesian mimicry system

Viceroys, the willow feeders, were long considered to be perfectly edible, palatable insects that gained some protection by their resemblance to the emesis-producing monarchs.  In a series of clever experiments, lepidopterist and evolutionary biologist David Ritland showed back in the 90’s that in some areas like south Florida, viceroys are actually more distasteful and unpalatable to bird predators than co-occurring populations of monarchs or closely related queens.  The monarch and queen larvae in these areas feed mostly on species of milkweed (Asclepias tuberosa, Sarcostemma clausum) that have very low concentrations of cardenolides, leaving the danaid butterflies (monarchs and their relatives) relatively palatable.  The viceroys, by contrast, sequester toxic phenolic glycosides from their willow hostplants.  When abdomens of viceroys and queens were offered to predatory birds (red-winged blackbirds) in the lab, the birds rejected the viceroys more often than they did the queens.  So in some areas, viceroys are apparently the more distasteful model (or co-model, in a form of shared aposematism called Mullerian mimicry) and monarchs and queens the more palatable mimics.

Viceroy with wing damage suggestive of a predator attack.  Notice the symmetrical chunks missing from both hind wings, and the V-shaped pieces missing from the left wings.  Most likely, a predator (bird, lizard?) grabbed the wings while this butterfly had them folded.

Viceroy with wing damage suggestive of a predator attack. Notice the symmetrical chunks missing from both hind wings, and the V-shaped pieces missing from the left wings. Most likely, a predator (bird, lizard?) grabbed the wings while this butterfly had them folded.

So maybe in science, as in life, a little humility is a good thing.  It’s often the case that we don’t understand complex natural systems as well as we think we do on first consideration.

Female common yellowthroat  in red maple.

FOS birds and what they’ve taught me

October 6, 2013

For those who aren’t at least mildly manic about all things birds, FOS stands for First Of Season.  In both migrations, I look forward with great anticipation to each and every FOS, as do most birders.  We’re all addicted to the thrill of the new, even if it isn’t truly new.

House wren scolding me for no apparent reason.

House wren scolding me for no apparent reason.

My first real field guide when I became interested in birds was the venerable Golden Guide to North American Birds, by Chandler Robbins et al.   A truly revolutionary field guide in so many ways, and still one of my favorites.  For the first several years as I was learning northern Virginia birds, I made a note of the FOS date in my copy of Robbins (which I still have, dogeared and held together by duct tape) of the migrants that I saw regularly.  After a few years, a remarkable fact became apparent to me – the FOS dates for many species were stunningly regular and predictable, sometimes within a day or two of each other each year.   So the first thing FOS birds taught me was that the natural calendar has a great constancy about it.   Not exactly a world-changing revelation, but it seemed so to me at the time.  I could actually anticipate and savor the idea of seeing some of my favorite birds at a fairly specific time each year.

Male bobolink in breeding plumage.  Emeralda Marsh Conservation Area

Male bobolink in breeding plumage. Emeralda Marsh Conservation Area

These days FOS birds fall into two fairly distinct groups for me.  One comprises the transient migrants, who will pass through in a fairly short period of time, not to be seen again until the next migration, or in some cases, until the next year for species that shift their migratory pathway between fall and spring.  These transient migrants are always a thrill, partly because of the ephemeral nature of their passage.  In Florida, the species that epitomizes this group for me is the bobolink, which I typically see in Volusia County for only a couple of weeks, beginning in late April and extending sometimes to the second week of May.  I can’t think of many sights or sounds that stir my heart more than a flock of hundreds of bobolinks, males in full breeding plumage and constant boisterous song, working their way through a wet successional field in synchrony, disappearing and then leap-frogging each other in methodical waves.  The beauty of the transient FOS species is quite obvious – they will soon be gone, not to be seen again until another half-year rolls by.

Gray catbird.  Lake George State Forest

Gray catbird. Lake George State Forest

But the more informative group of FOS bird is for me the winter residents.  Especially in Florida, where we are gifted with such a rich and diverse wintering bird fauna, these birds can appear any time between mid-summer (prairie warblers, for example, a few of which will remain to winter here) and late fall-early winter (huge flocks of American robins and cedar waxwings come to mind).   Throughout fall migration, the anticipation of newly arrived winter residents is a powerful motivator to entice me into the field.  Right now, we are in the midst of a mini-wave of arriving winter residents – I saw my FOS common yellowthroats, house wrens, eastern phoebes, palm warblers, and gray catbirds in the last week or two.

Male common yellowthroat in a red maple swamp.  Lake George State Forest

Male common yellowthroat in a red maple swamp. Lake George State Forest

Palm warbler, western subspecies.  Heart Island Conservation Area

Palm warbler, western subspecies. Heart Island Conservation Area

Here’s what FOS winter residents have taught me, and reteach me every year.   There is immense beauty and joy in the plain and the regular.  House wrens are a case in point.  Not the most strikingly beautiful passerine, unless you’re really into brown, drab birds, but what they lack in superficial glitz they make up for in attitude and belligerence.   Within a couple of weeks, I will inevitably begin to take these scolding little scuts for granted, much as I habitually do with most of our common permanent residents.  I see this dynamic played out in others every time I teach Ornithology.   Within a week or two after the semester has begun, as we begin to accumulate a respectable species list, even the newly minted birders in the class begin to develop this unconscious devaluation of common birds.  Even spectacular common birds.  I’m sure this thought has been shared by many others, but I tell these nimrods every semester that if one saw a northern cardinal only once in her life, for most it would be an incomparably treasured memory.   I still vividly recall the reaction of Sabrina Krisberg, an enthusiastic student from over a decade ago, when she got her first look through binoculars at a male cardinal in rich early-morning light.   She slowly whispered in a voice full of awe and reverence, “It’s so perfect”.

Female common yellowthroat.  Lake George Conservation Area

Female common yellowthroat. Lake George Conservation Area

Male common yellowthroat.  Heart Island Conservation Area

Male common yellowthroat. Heart Island Conservation Area

So even though I know the magic and exhilaration of seeing a FOS bird each fall is transitory, and within weeks I will be shrugging off house wrens and gray catbirds, their appearance each fall teaches me again that there is immense beauty and spectacle right in front of me every day.   It’s so easy to become complacent and jaded by the familiar, of every sort.  I hope that these sometimes plain, and often obscenely abundant (think yellow-rumped warbler here) FOS birds remind me each season not to take any of this beauty for granted.   The beauty of my everyday life – a job I (mostly) love to go to each day, the wonderful friends I love so deeply, and good people in general;  it’s far too easy to forget how incredibly fortunate and privileged I am for the many gifts that surround me every day.

Eastern phoebe.  Lake Dias Cemetery

Eastern phoebe. Lake Dias Cemetery

And it’s all so vanishingly brief.  I’m no Roy Batty, but I fully understand what he meant.  I’ve never seen attack ships on fire off the shoulder of Orion, but I have seen FOS house wrens chattering at me from a thicket in October.    And as my friend John Jett is fond of saying, that’s a beautiful thing.

Female common yellowthroat.  Lake George State Forest

Female common yellowthroat. Lake George State Forest