BIRDING BY HINDSIGHT: A Second Look at Dowitchers
So, you say you've been studying dowitchers for years and still can't tell a Long-billed from a Short-billed? Is that what's bothering you, Bunkie? Well, join the club! If it's any consolation, you're not alone, and this writer has long been just as clueless as the rest of you. Even now, after doing some research into this ID problem, I seem to be more lost than ever, discovering references which present more questions than answers.
It's not hard to see why dowitcher ID has been a problem for so long. Decades ago, Short-billed and Long-billed dowitchers used to be considered one species. Then, after they were split, we were left to consider four ID problems, not just two, since there are three Short-billed subspecies which can look more distinct from each other than they do from Long-billeds. (Actually, there are really a dozen sets of plumages to consider, with basic, alternate, and juvenile plumages for each of those four forms!)
And don't count on the field guides to be of much help. Consider that your Geographic field guide has presented no fewer than three different versions of dowitcher ID in its four editions (only the third and fourth editions are the same). Consider as well that the original 2000 Sibley field guide presents somewhat different dowitcher information than do its later Eastern and Western regional offspring. Clearly, this is one of those many complex identifications which no field guide can adequately handle.
Well, when the field guides fail you, as Hindsight readers are well aware, aren't the answers found in those in-depth ID articles which regularly appear in journals like North American Birds and Birding? Hardly. The former journal (and its predecessor, American Birds) has never had a single article on dowitchers. The only time Birding presented an article addressing overall dowitcher ID was back in 1983 (Birding 15:151-166), long before some important field marks were uncovered. And a recent article by Caleb Putnam, "Fall Molts of Adult Dowitchers" (Birding 37:380-390), only addresses the single subject of ID-by-molt during fall migration, and some shorebird experts disagree with its conclusions.
Kenn Kaufman's book A Field Guide to Advanced Birding came out in 1990 with a chapter contributed by Claudia Wilds, one of the authors of that 1983 Birding article. Basically the equivalent of a journal article, it presents mostly accurate information, although it oversimplifies some field marks, and ID points discovered since 1990 are not included.
Similarly, bird books devoted to shorebird identification have been outdated and few in number. Until last year, the only comprehensive guide was Shorebirds: An Identification Guide to the Waders of the World by Hayman, Marchant, and Prater. This otherwise excellent book, however, came out 20 years ago and fails to adequately clarify the dowitcher ID problem. Indeed, Alvaro Jaramillo and Brian Henshaw, authors of a later article on dowitchers (Birding World 8:221-228), consider that book's illustrations of Short-billeds in alternate plumage to be inaccurate.
In 2005, Dennis Paulson came out with Shorebirds of North America: The Photographic Guide. However, as excellent as this book is, its dowitcher treatment is incomplete and somewhat inconsistent with other references. And due for publication later this year is Shorebirds of North America, Europe, and Asia by Stephen Message and Don Taylor. Perhaps this book will have all the answers, but, given the history of other dowitcher references, I'll be surprised if it does. [Author's Note, August 2016 – A more recent and recommended reference on dowitchers and other shorebirds is The Shorebird Guide by O'Brien, Crossley, and Karlson.]
In recent years, of course, websites have become all the rage, and there are several devoted to bird identification. Surprisingly, though, with one exception, all of these – even those presenting excellent information on other complex ID issues – either mention dowitchers only in passing or avoid the subject entirely.
Surfbirds.com is the only website I've found which includes an attempt at a comprehensive (but not necessarily accurate!) analysis of dowitchers – http://www.surfbirds.com/ID%20Articles/dowitchers1005/dowitchers.html. The authors, Cin-Ty Lee and Andrew Birch, apparently have plans for this information to be expanded into an article in Birding. It remains to be seen, though, whether that article will successfully advance our ID skills. More on this later.
Well, against my better judgment, here goes. I preface this list of dowitcher field marks with three comments. First, any information on Short-billed Dowitchers refers only to the hendersoni subspecies, the only form which apparently breeds in central Canada and migrates through Minnesota (but see below). The western subspecies caurinus and the eastern subspecies griseus, which in alternate plumage can look quite different from each other and from hendersoni, have apparently never been recorded in or near Minnesota.
Second, there is no need here to discuss coastal habitat preferences of wintering and migrant dowitchers: i.e., Long-billeds usually in fresh water; Short-billeds only in salt water. This difference does not apply to inland states, so don't assume Salt Lake in Lac Qui Parle Co. excludes Long-billeds and is the only Minnesota site for Short-billeds. (By the way, in Texas I see and hear wintering Long-billed Dowitchers all the time in salt water; some references try to claim they are only in freshwater habitats.)
And, third, you'll quickly see that my expertise and most of these field marks leave a lot to be desired....
Dowitchers in Alternate/Breeding Plumage
• The sides of the neck and upper breast on fresh-plumaged Long-billeds tend to be more heavily marked and barred than on Short-billeds, as shown in Sibley and the 3rd or 4th editions of Geographic. (But beware the inadequate treatment of this in the first two Geographic editions and in Advanced Birding.)
This feature, however, depends on how fresh or worn the plumage is and whether it has completely molted in. It also may apply to other parts of the underparts: some references say it does; others say just the sides of neck and upper breast show a difference. Whatever. In any event, beware plumage wear, incomplete molt, and individual variation.
• The upperparts of fresh-plumaged Long-billeds tend to look darker overall (back, scapular, covert, and/or tertial feathers mostly black mixed with chestnut) than those of Short-billeds (black mixed with broader and paler buff areas). Again, see Sibley and Geographic edition #3 or 4. Like the underparts, however, all this varies with wear, molt, and the individual bird.
• Some references, including Putnam's article on dowitcher molt (see above), claim that only Long-billeds molt during fall migration, while Short-billeds molt after reaching their coastal wintering grounds. If true, this would help a lot: any molting or basic-plumaged dowitcher here in summer or fall would thus have to be a Long-billed, since all adult Short-billeds then would still be in alternate plumage. The catch, however, is that other authorities consider these conclusions on molt to be tentative at best.
• Our perceptions in Minnesota and vicinity of Short-billed Dowitcher ID have long relied on the assumption that only the hendersoni subspecies nests along the west and south sides of Hudson Bay and would be the only form migrating through the Midwest. However, as stated in Jaramillo and Henshaw's Birding World article, Short-billeds breeding in Churchill also apparently include the griseus subspecies and birds intermediate between griseus and hendersoni. If true, are we also seeing migrant griseus individuals here, which would look different from hendersoni birds?
Dowitchers in Juvenile Plumage
• As any birder with some dowitcher knowledge is aware, the juvenile plumages are easiest to distinguish: i.e., plain tertials and duller grayish-brown underparts = Long-billed Dowitcher; patterned tertials and brighter buffy-orange underparts = Short-billed.
Simple, right? Sorry, but there are three caveats. First, it's not so easy to distinguish a juvenile Short-billed from an adult of either species: so, if you see a dowitcher with patterned tertials and brightly-colored underparts, it could still be an adult Long-billed. Second, the references disagree on whether or not that pattern difference on the tertials also applies to the scapulars: i.e., some say that patterned scapulars = Short-billed; others say such scapulars = either species. Third, if you have a copy of Paulson's book, look at photo 82.15 on page 315: even the author concedes that this juvenile he labels as Short-billed Dowitcher may well be a Long-billed! (If an expert like Paulson can be confused by this "easiest" of the dowitcher plumages, is there any hope for the rest of us?)
Dowitchers in Basic/Winter Plumage
• An unstreaked whitish chin or throat is more indicative of Short-billed Dowitcher, while a streaked, grayer chin suggests a Long-billed. At least some references agree on this, anyway, while others (e.g., Sibley) don't mention or illustrate any difference. Of course, exceptions and intermediate patterns exist, and I can show you at least one Long-billed photo showing an unambiguously clear white throat.
• A Short-billed's breast tends to look mostly pale with grayish spotting or mottling, and its lower edge is not clearly delineated. Conversely, a darker and more solid gray breast with a sharper lower edge tends to indicate a Long-billed. Here, as well, however, there are exceptions, intermediates, and hard-to-see chest patterns.
• Even less reliable are dowitcher flanks: often darker and more solid on Long-billeds; paler and more barred on Short-billeds. While this latter pattern seems to hold true on most Short-billeds, I have seen too many photos of Long-billeds with this same appearance.
• Turning to the upperparts, a Long-billed's feathers typically have darker centers with often broad grayish-brown borders; these same feathers on a Short-billed tend to be paler, more uniform, with crisp narrow white edges. Predictably, though, none of the field guides illustrates this, not even Sibley, and I have seen several photos showing ambiguous upperparts patterns. One confusing aspect of this field mark is that Paulson's guide states the difference is limited to the back feathers, while other references suggest the distinction is in the scapulars and coverts.
Dowitchers in Any Plumage
• Finally, a field mark we can all agree on: dowitcher calls! In fact, this is about the only single diagnostic feature in dowitcher identification: the thinner and higher-pitched "keek" (or a repeated "keek keek keek") of the Long-billed, compared to the lower-pitched and yellowlegs-like "tu tu tu" of the Short-billed. If not heard well, the multi-syllabled version of the Long-billed's call might suggest a Short-billed, and a Lesser Yellowlegs' call in the vicinity could be mistakenly attributed to that silent dowitcher nearby, but otherwise ID-by-vocalization is pretty straightforward. (Of course, both dowitchers can remain stubbornly silent!)
• Time-of-year considerations can be nearly as diagnostic as vocalizations, since Long-billeds migrate earlier in spring and later in the fall than Short-billeds. At Minnesota's latitudes, any dowitcher you see before late April or after mid-September would almost certainly be a Long-billed, while a dowitcher from late May to mid-July should be a Short-billed by default. Of course, there are times when both species are passing through (late April to mid-May, and late July to mid-September), and then the calendar won't help.
• Despite their names, only extreme examples of long or short bill lengths might suggest which species you're looking at, and even then direct size comparison is advised. There is considerable overlap, so be prepared to ignore bill length as a field mark most of the time. By the way, a Long-billed's legs are also longer on the average, but, again, there's lots of overlap, and only extremely long or short legs might be of ID assistance. (Note that the female dowitcher's bill and legs are longer than the male's.)
• Speaking of bills, Lee and Birch in their Surfbirds.com analysis claim that a Short-billed's bill typically looks slightly but noticeably decurved, while the Long-billed's is straighter. While these authors probably know a lot more about dowitchers than I, they have some explaining to do. If what they suggest is true, why have I seen so many photos of Long-billeds with decurved bills and so many Short-billeds with straight ones? Consequently, I certainly fail to see how bill shape amounts to even a minor supporting field mark.
• There is another aspect of shape, however, that involves dowitchers and seems much more consistent: the body profile of feeding birds. As a Long-billed probes vertically, note its "humpback" body profile, with a nearly 90% angle where the back meets the neck, and a strongly concave shape where the back meets the tail. Probing Short-billeds have a flatter profile and less of a humpback appearance. I would assume, however, that this profile difference won't hold up for every single individual, and note this field mark should only be considered on dowitchers when in probing mode.
• Primary extension is also mentioned in some references as a helpful field mark, with the Short-billed's wings longer than the Long-billed's. Any difference, however, is slight and hard to detect. More importantly, there is disagreement over how to measure this extension, and, of course, there are photos which reveal inconsistencies.
The Birding World article says to consider the wing tips relative to the tail: i.e., wing tips beyond tail = Short-billed; wing tips short of tail = Long-billed; wing and tail tips equal = either species. But Surfbirds.com and Paulson say the extension is relative to the tertial tips: wing tip extension beyond tertials = Short-billed; no extension = Long-billed. But perhaps Sibley shows it best with three Long-billed illustrations: one with the primary tips beyond the tail tip, one with primary and tail tips equal, and the third with primaries short of the tail tip! Sometimes inconsistency is the reality.
• Dowitcher watchers have long considered tail barring to be worth noting. If you can clearly see the actual rectrices (which isn't easy since folded wing tips get in the way; and make sure you're not just looking at the tail coverts), you probably have a Short-billed if the white bars are obviously wider than the black ones. Otherwise, you're out of luck: both dowitchers can have equal-width bars or black bars wider than the white. (Some references erroneously claim that wider black bars only apply to Long-billed Dowitchers.)
• The Surfbird.com treatise on dowitchers makes a big deal about something they call loral angle. Don't ask. The illustrated difference in this between the two dowitchers is so slight that I fail to see how this alleged field mark could ever be useful, and I am unable to find any clear or consistent differences in any of the photos.
• Nor do I see any validity in Surfbirds.com's claim that there is anything worth considering in a dowitcher's supercilium or eyebrow. Lee and Birch claim that a Short-billed's eyebrow is "arched" as it curves up over the eye and widens in front of it, while a Long-billed's is relatively straight. If so, how do they explain the numerous photos I've found showing Long-billed Dowitchers with clearly arched eyebrows and Short-billeds with straight ones?
Again, with all due respect to Lee and Birch, their assertions about decurved bills, loral angles, and eyebrows seem tentative at best, quite inconsistent with the photographic evidence, and in need of serious clarification. At worst, they are counterproductive – making dowitcher ID not easier, but more confusing than ever!
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To make a Long-billed story Short, a basic tenet of accurate bird identification, especially when dealing with difficult birds, is to consider a combination of field marks. And if ever there was a time when this applies, it would be when looking at dowitchers – especially since the reliability of so many field marks is open to question.
Or, you may just want to stick with the calendar, and hope the next dowitcher you see is in early April or October (a default Long-billed) or in June (a Short-billed). Either that, or wait for it to say keek or tutu. Otherwise, we'll just have to hope the new Message & Taylor book or that Birding article promised for later this year adequately address all our uncertainties.
And that's the Long and the Short-billed of it.