A Busy Night Sky: Things that go "tseep" in the dark

"First Fall Swainson's Thrushes heard overhead this morning at 5:15AM. Right on time."

This welcome post was shared by Portlander Wink Gross on Oregon Birders Online (OBOL) on 24 August 2011.

It may sound counter-intuitive, but one of the best ways to appreciate the raw numbers of songbirds migrating through your area is to go outside at night. While you may be able to see lots of migrants during daylight hours, the number of migrants that one can hear during their nocturnal flights is often exponentially greater. I can safely say that I've never seen more than 500 Swainson's Thrushes during any single fall migration season, but there have been many nights when I've heard more than 500 nocturnal Swainson's Thrush call notes in the span of 15 minutes...or less. Although the number of actual birds these calls translate to remains a bit of a mystery, I've always assumed that I'm not hearing any single thrush call more than 4-5 times as it flies over.

When conditions have been ideal--generally dense overcast, which results in low-flying birds--I've spent up to an hour listening to the non-stop (at least 20 calls/minute) nocturnal vocalizations of Swainson's Thrushes. When I start doing mental extrapolations, the potential number of birds passing overhead on such nights becomes staggering.

In the grand scheme of things, I live in a rather depauperate nocturnal soundscape. First, I'm stuck in the American West, which offers neither the variety nor the shear numbers of migrant passerines that one might experience living in the eastern one-third of North America. Secondly, I live in the middle of Portland, Oregon's "urban surf" zone, thus just hearing the muted flight calls of many species presents a challenge. Despite these shortcomings, Portland does get good nocturnal flights of Swainson's Thrushes. During peak movements the fairly loud flight calls of low-flying Swainson's Thrushes may be heard at rates of 50+ calls/minute and, for brief bursts, the flood of airy "weep" calls (http://pjdeye.blogspot.com/2009/02/thrush-calls.html) can be so frequent that they cannot be easily counted.


This image shows the sonogram of a Swainson's Thrush flight call.  (Source: http://pjdeye.blogspot.com/2009/02/thrush-calls.html)

Last October I made my first pilgrimage to Cape May, New Jersey. Cape May is considered by many to be the best place in all of North America to experience the fall migration of songbirds. Many of the birders who call Cape May home have devoted much effort to the study of songbird flight calls. They and others have worked with the Cornell Laboratory of Ornithology to create  libraries of recordings of flight calls that are coupled with visual sonograms for these vocalizations. It's surprising how helpful it is to see the "shape" of each flight call expressed in a sonogram as you listen to and attempt to learn their differences. If you are blessed with good hearing, over time it is possible to start recognizing the unique subtleties of these vocalizations and use them to identify birds that you can't see in the night sky.

During our visit to Cape May, Shawneen Finnegan and I stayed with Michael O'Brien and Louise Zemaitis. On one particular evening I decided to go outside at about 11PM, just before we were all set to retire for the night. Though I hoped to hear some birds overhead, Michael, who is an authority on the flight calls of North American passerines, suggested that even on good flight nights he and Louise rarely hear more than a few calling birds directly over their house. Thus, I ventured outside with tempered optimism. To my surprise, within the first 30 seconds I heard no fewer than 15 unidentified call notes. I went inside and told the others that there seemed to be lots of birds passing overhead. Once outside, it took less than 15 seconds for Michael to announce, "we need to go to the Convention Center!"

The Cape May Convention Center is located along the beachfront boardwalk in the "downtown" section of historic Cape May on the southern tip of a long peninsula. The boardwalk and adjacent street are well-lit and parallel the Atlantic Ocean side of the peninsula just east of the mouth of Delaware Bay. During autumn flights, birds that are generally moving south or southeasterly tend to follow the coastline once they reach the Atlantic, putting them on a southwesterly heading as they move done the Atlantic side of Cape May. The Cape May boardwalk and Convention Center lie right below this nocturnal flight line at the southeastern corner of the cape.

After making the short drive downtown, the four of us spent the next hour sitting along the boardwalk as Michael called out one species after another, "Blackpoll, Palm, Black-throated Blue, Palm, Gray-cheeked Thrush, Swamp Sparrow, Indigo Bunting...and on it went. In all, we heard the flight calls of about 25 species of passerines, including those of Seaside Sparrow and Bicknell's Thrush, which only Michael recognized. In addition to the array of passerine vocalizations we heard, ambient light from the boardwalk illuminated the ghostly shapes of dozens of herons and egrets as they passed overhead in small groups. It was a spectacular experience, particularly for a Westerner unaccustomed to such flights.  

Back home in Portland, most of the nocturnal calls I hear are those of the Swainson's Thrush. It is a loud and fairly distinctive note that can be learned readily, so don't dismay if your hearing isn't perfect. Even if you don't hear or recognize any other flight calls, there will often be enough thrushes sounding off to keep you more than entertained. Over the next several weeks, look for nights with low overcast and venture out into the cool night air, or set an alarm to wake you about an hour before sunrise. If you happen to hit a good flight, it will surely change your notion of what is happening in the night sky as you sleep.

Here are some additional links to online resources if you are interested in learning more about nocturnal flight calls:





A Picture is Worth a Thousand Birds!

The Perception Game: Knowing What You Know vs. Seeing What You Are Looking At


This is the photo used in the online bird ID quiz described by this article. (Photo by Mark S. Szantyr)

The advent of affordably-priced digital SLR cameras and the technological advances in digi-scoping have made documentation of rare birds much easier than it has been in the past. Even if you do everything wrong, these cameras and optical technologies are so smart and so forgiving, that you will likely still come up with an identifiable image. That being said, Greg Hanisek and I were talking one night and we hatched a plan. Our idea was to offer a properly exposed, extremely sharp image of a very common bird in a less than ideal pose and see how many birders can get the identification right. 

In order to be fair, we chose an image that provided several identification clues. Our discussion and this experiment arose after a rash of shorebird photos on the web caused an international tsunami of mistaken identifications, ID dogma, vitriol, and lunacy. This photo quiz was not designed to disparage the identification skills of the birding community in any way, nor did we wish to demean the great discussion of identification that was being hashed out on the web. More, we were curious about how good, even great birders process the visual information provided in record photos. 

I had a photo that I thought would be a good choice. I showed it to Greg and he agreed that it was the one. The fact that he had a modicum of difficulty with the identification at first made it all the better for us. Greg published the photo in his natural history blog provided under the auspices of the Republican-American Newspaper in Waterbury, Connecticut. Aside from revealing that the bird was photographed in Connecticut, he offered very little support information other than to point out that I was both diabolical and cruel. While his character assessment may be true, I didn’t believe that this identification challenge would be as hard as it proved to be. 

As the answers (let’s call them guesses) filtered in, the list of species and genera involved grew and grew. I was gobsmacked by the range of possibilities being offered. The bird in the photograph is one of the most common birds in North America. My friend Dave Irons, a birder from Oregon who is the content editor for BirdFellow.com, says that the juvenile plumage of this species may be “the most mis-identified bird in North America”. Quite a claim. But after this, I think he might be right. 


Here's image of an immature Black-crowned Night-Heron in roughly the same position as the bird in the quiz photo. Notice any differences? (Photo by Mark S. Szantyr)

Leading contenders in this identification sweepstakes(?) were immature Black-crowned Night-Heron (why not Yellow-crowned Night-Heron?) and immature or female Green-winged Teal (why not the other teal in this group?). Virtually no one came up with the correct answer. The bird in the photograph is a passerine. How could the size and structure of this bird be so mis-interpreted? 

References were made to the large, flat, duck-like bill. No bill is visible in the photograph. Many people talked about the thick legs (?), yet no one seemed to notice or mention the one exposed passerine-like toe. The tail, while mostly obscured, does show a decipherable basal shape and allusion to structure, none of which is right for a duck or a heron. Some thought that the bird was sitting on large rocks, causing us to wonder how the size of the rocks was determined from what is available in the photo.


One of the many incorrect guesses for the identity of the mystery bird was Green-winged Teal. Compare this actual Green-winged Teal with the color, pattern, and shape of the bird in the photograph at the top of this page. (Photo by Steven Mlodinow)

So, how does this happen and how often? Are we all (and I include myself in this question) so lax in our observational skills that we see what we want to see rather than what is right in front of us? Do we see one thing that we think we recognize and force the remaining details to fit our first assumption? If only provided a quick glimpse of a bird, perhaps it is more understandable, though no positive ID should be made on this kind of sighting. The annals of birding legend are full of situations where the first wishful identification started all observers down a garden path that resulted in a lemming-like plummet into the sea of OOPS! I am reminded of a Smith’s Longspur in California, a Northern Hobby in New York, a Little Egret in Connecticut, and oh so many other subsequent heartbreaking moments in birding. We all go over the edge not only willingly, but gleefully, especially when presented with the opportunity to bask in the golden sunlight of one more twitch on the lifelist. How quickly sunlight can turn into sunburn! This quiz offered more than a quick glance. Observers could study the image at their leisure. There was no danger of it flying off. 

So how does one assess a bird sighting? How does one assess a seemingly good photograph of a reported bird, whether it be a suspected rarity or not? 

Carefully is the easy answer. Totally is another. 

Was our photo unidentifiable? This is an interesting question and a valid answer might be NO for some observers. Does experience come into play here? Is it identifiable only when compared to patterns in one’s experience? Did I know what this was because it fit a match to something I have stored in my memory banks? This could be part of the answer but I don’t think it’s the entire answer.
As I state above, the two most shocking responses were immature Black-crowned Night-Heron and female Green-winged Teal.  Other responses ran the gamut from various sparrows to Pine Siskin.  American Pipit was mentioned once.  Two people, one a bird-bander and another, a bird-rehabilitator, got the correct answer.  

Looking at the photo provided, one can ask several questions to begin the process. How big is the bird? To which family of birds does the unknown belong? As mentioned before, there is one toe visible in the photograph. It is a very passerine-like toe and once noting this, the legs, which are visible, become very passerine-like in thickness and in length. More careful observation will show that the base of the tail is visible between the bird’s legs. The tail seems to flair out from the base, again, reminiscent of a songbird tail and not like that of a heron or duck. A look at the feathers shows fresh edging commensurate with new feathers…likely a bird of the year or a bird just recently molted. The extent of the fresh edging to all feathers visible pushes the identification to a juvenile or first year plumage. The relative length of the wings compared to the overall size of the bird can be extrapolated from what is visible of the greater coverts and primaries. The pattern of streaking on the under parts and the crown feathering differs significantly from that of the juvenal-plumaged Black-crowned Night-Heron shown above and with that of a female teal. 

Our quiz bird is a juvenile Brown-headed Cowbird.  It is likely that if this bird was in the same pose in a woodland or at a bird-feeder, more people would have come up with the correct identification.  It is striking how much the context of the bird had to do with how it was identified.  This youngster was chasing a Song Sparrow through large granite boulders scattered along the southeast Connecticut coastline, begging food for all it was worth.  It was at times completely oblivious to my presence.  I was able to study it at my leisure.


The images above and below offer two additional shots of the quiz bird striking more identifiable (???) poses. Young Brown-headed Cowbirds may superficially resemble a number of species, but when one combines the general appearance, the rather heavy, conical bill, and size--larger than a House/Purple Finch or a sparrow and smaller than blackbird--there are no North American species with which they should be confused. But, given that most songbirds retain their juvenile plumages for only a matter of weeks, most of us don't see them often. Clearly, this provides limited opportunities for us to learn these temporary plumages. (Photos by Mark S. Szantyr)


If I were to break down every aspect of structure and feathering, I might be able to absolutely identify this bird from the photograph.  Then again, I might not.  Yet in the field I knew this bird. If I had been given this quiz, I believe I would have gotten it right because I spend a lot of time studying birds and because I have been blessed with a good memory.  But memory is not enough.  In fact, memory can be misleading.

There has been a fantastic discussion on the web dealing with perception, experience, and bird-study.  The way we identify birds is a complex and intricate balance of all of these things.  It is possible to hone ones abilities in each of these areas.  Certainly, more time looking at birds and more time studying birds in the field and in the literature helps with two of these.  But what about perception?  

As an artist and educator, I teach students to draw from life every day.  I teach them to look at an object and translate the three-dimensional reality to a new two-dimensional reality by using their ability to perceive, interpret, translate, and communicate.  Very often the first attempts show a lack of ability and often a lack of trust in their ability to accurately perceive what is in front of them.  By constant practice, by looking, seeing, drawing, correcting and then repeating this process over and over, students learn to draw.  More importantly, they learn to see.  

Carrying a sketch book or note book the field while birding allows an observer to use the same methods described above, seeing, studying, sketching and checking the sketches and notes, to arrive at a confidence in one’s abilities and in that identification.  Does it end there?  No.  To repeat this process each and every time ensures that one’s perception is still accurate. And sometimes, by checking and double checking, you find something that you did not expect.  The reward for this work is learning something new about a common species or uncovering a rarity.  Perhaps my favorite feature of the new Crossley Guide to Bird Identification is the wide range of views he offers of birds in the acts of being themselves.

In the classroom, I use this analogy.  I tell my students that, rather than being eagle-eyed, I prefer that they were like dogs.  Dogs walk into a room, perhaps a room they enter every day of their lives, and the smell everything, over and over, just to be sure they know what they know.  We should bird like dogs…visually ”sniff” every bird, over and over, take notes, and commit these notes to study, and then sniff again to be sure.

Messy vs. Neat: Ageing Southbound Migrant Shorebirds

Unlike most species of birds, shorebirds (sandpipers and plovers) retain their juvenile plumages through much of their southbound (Fall) migration, thus in order to properly identify them it's important to first determine whether you are looking at an adult or a bird of the year (juvenile). If by chance you find and report a rare shorebird from a local mudflat, before asking anything else, your local field notes editor will want to know, "was it an adult or a juvenile." For many birders, even some with years of experience, this can be a stumper. Here's an easy first step to start learning how to make such determinations.

Since the majority of you reading this article live in the mid-latitudes of the Northern Hemisphere, let's first consider the timing of shorebird migrations where we live. Many of our familiar species of shorebirds are high-latitude breeders that nest near or inside the Arctic Circle. Their breeding season occupies a narrow window from very late May to early July. Once breeding duties are completed, adults don't linger long on the breeding grounds, thus southbound adults of many species can be seen back in the mid-latitudes (southern Canada and the Lower 48) by late June or early July and they will, in many cases, arrive on their wintering grounds by early August.


This adult Sanderling was photographed on 24 August. Notice how messy the plumage is and how there is no consistent color pattern to the upperparts. The dark centered feathers are remnants from the breeding or alternate plumage, while the paler gray feathers are part of the winter or basic plumage that is just growing in. This bird is in the process of molting. Also note the differences in the lengths of feathers that are side-by-side and how these feathers don't lay together smoothly. (Photo by Glenn Bartley)


This juvenile Sanderling was photographed on 4 September. The first thing you'll likely notice when comparing this bird to the adult in the image above, is how neat and orderly the plumage looks. All of the feathers on this bird were acquired during the same molt, thus they are consistent in color and size and they lay together smoothly. It shows no indications of molt in progress. (Photo by Glenn Bartley)

Their offspring are left behind on the breeding grounds to fatten up and complete the acquisition of their first complete set of feathers (juvenile or juvenal plumage). The first juveniles normally start  appearing Lower 48 and southern Canada at the end of July, about the time the last of the adults is moving through. After about the 10th of August or so, the bulk of the shorebirds one sees at mid-latitudes will be juveniles. There are exceptions to these generalities, most notably species like Black-bellied Plover, Dunlin, and Long-billed Dowitcher, all of which are later fall migrants.


By the time southbound adult shorebirds reach the mid-latitudes they will be in the midst of their prebasic molt, thus they are replacing feathers as they migrate. The basic or winter plumages of shorebirds are generally much duller (often cold gray tones) than the bright richly-colored alternate plumages they wear during the breeding season. So, as the new feathers grow in, the contrast between the old and new feathers is often quite conspicuous, creating a calico or mottled look. Since they are on the move, they can't replace all their feathers at once. Hence, this protracted molt may result in side-by-side feathers showing significant differences in  size and shape. 


This close-up view of the wing coverts of a molting adult Sanderling shows feathers that vary greatly in terms of length, overall size, and shape. As a general rule, the covert feathers on adult shorebirds are larger and generally more elongated than those seen on juveniles of the same species. They also don't seem to be arranged in the tract rows one expects to see when the molt has been completed. (Photo by Glenn Bartley)


When the first juvenile shorebirds show up at the local mudflats they will be in extremely fresh plumage that is likely no more than 4-6 weeks old. It will be several more weeks before they start transitioning from this juvenile plumage to their first basic or first-winter plumage. You won't see any of the color irregularities and inconsistency in pattern that is evident in adults at this time of year. Since the juvenile feathers are fully grown by the time they leave the breeding grounds, side-by-side feathers in the scapulars and coverts will be roughly the same size and shape and they will lay together in an orderly fashion. The overall plumage will look very smooth and uniform, with nothing out of place.


This close-up of the wing coverts of a juvenile Sanderling shows rows of feathers that are similar in size and shape and show consistent color pattern. Note the orderliness of the individual rows of feathers. As is clearly evident in this image, the covert feathers of juveniles are typically smaller and more rounded than those of adults. (Photo by Glenn Bartley)


Juvenile plumages are unique to hatch-year birds. In the majority of shorebird species the first complete feather sets are retained through most of the fall migration. The period of overlap when one is likely to see adult and juveniles together is fairly narrow for most species. While there are no absolutes, as a general rule if you see a southbound shorebird (July-September) whose plumage appears messy and inconsistently patterned, it is an adult. If, during this same time frame, you see a wader whose plumage is very neat and consistently patterned, then it is likely a juvenile.


In this image, taken at Madison, New Haven Co., Connecticut on 11 August 2011, we can directly compare a juvenile (left) with a transitioning adult (right) Short-billed Dowitcher (subspecies "griseus"). Defying conventional wisdom, juvenile shorebirds are typically brighter and more colorful than adults at this time of year. (Photo by Mark S. Szantyr)

To some, this may seem like an over-simplification of a complex identification issue, a point I would agree with on some level. At the same time I think it is important to keep in mind that the average birder may spend only a few hours per fall birding in habitats that allow them to study these differences. They may not grasp the difference between the scapulars and the coverts or know where to look to see a tertial feather. What is learned one year may well have to be relearned the following Fall. My hope in writing this piece was to offer one easy to remember nugget that can be retained. If we can at least help others learn to age these birds properly, we drastically reduce the number of plumage options that they must sort through as they endeavor to identify fall migrant shorebirds to species.

Unplanned Obsolescence: Keeping Up With the AOU

Those who author and publish printed field guides must await reports from the American Ornithological Union (AOU) Checklist Committee with some degree of anxiety. In most years the reshuffling of the taxonomic deck is relatively minor, a common name change here, a species split/lump there, perhaps slight modifications to a few scientific names. While most of these changes in nomenclature and classification are low-impact to rank and file birders, they render our field guides instantly and irrevocably out of date.  


Nashville Warbler is one of several North American species formerly assigned to the genus "Vermivora." (Photo by Glenn Bartley)

We don't mind so much when a species is split (i.e. Pacific and Winter wrens), allowing us to add a life bird without getting out of the chair at our computer desk. Conversely, we don't take kindly to losing one of the few Latin words that we can readily pronounce, then seeing it replaced by a word that leaves us sounding like the lisping "Winthrop Paroo" (played by a very young Ronnie Howard) in the 1962 film version of "The Music Man."

Vermivora, the former genus for common North American warblers like Tennessee, Orange-crowned, and Nashville, rolls off the lips. It may be decades before I can say Oreothlypis without getting my tongue stuck between my teeth. I'm betting that North American birders will adopt a handy abbreviation (i.e. "Empids" instead of Empidonax) when dealing with this difficult to pronounce genus. Are the birds assigned to Oreothlypis destined to become simply "Oreos?"

While Vermivora persists as the genus for two extant North American species (Blue-winged and Golden-winged Warblers) and the presumed extinct Bachman's Warbler, the 52nd Supplement to the AOU Checklist (AOU Checklist Committee. 2011) was not so kind to Dendroica, which at 21 species was the most populous genus of  birds in the U.S. and Canada. It has been "deleted." The assortment of highly colorful and beloved warblers that formerly fell under this heading have been moved to Setophaga, which may not be as the tough to say as Oreothlypis, but is far less pleasant to the ear than Dendroica. I'm guessing that more than a few of us will find it difficult to eliminate the newly declassified "Dendroica" from our vernacular. 

As the content editor for this website and more specifically our online "social" bird guide, I've come to appreciate how these changes impact the works we publish. One of the beauties of online publishing is that all manner of updates and changes can be implemented quickly and painlessly. My occasional typos in this journal are usually discovered within an hour or so by either my mother or David Fix and are thus fixed within a few hours of publication. We are committed to making sure that the BirdFellow Bird Guide will be among the first resources to be updated when AOU revisions are released. The changes mandated by the 52nd Supplement have already been made to our guide, whereas, ironically, Black-throated Blue Warbler is still listed as Dendroica caerulescens on the AOU's own website.


I can only imagine how exasperating it must be for David Sibley, Don and Lillian Stokes, and the editors of the National Geographic Society series to see years of work and attention to every detail undone by revisions to the AOU Checklist. If you go out to buy a printed field guide today you will not  find a single one on the shelves that is current with these changes. How long will we have to wait to before a book that includes these nomenclature changes is available and how soon after will that volume be dated?

Literature Cited:

AOU Checklist Committe. R. Terry Chesser (chair) et al. 2011. Fifty-second Supplement to the American Ornithologists' Union Check-list of North American Birds. The Auk 128(3):600-613.