BIRDING BY HINDSIGHT: A Second Look at Shorebirds
[Author's Note, August 2016 – When this Hindsight article was first published in The Loon, several errors appeared as a result of the proofreading and typesetting; these were not in the original version as written and have been corrected here.]
Yes, we all know how hard it is to tell one hawk from another. Even worse, of course, are those dreaded immature gulls. But just as bad is a silent Empidonax flycatcher. Before you know it, those confusing fall warblers will be passing through. And who can tell all those sparrows apart?
As mystifying as those birds to identify, there is perhaps another group every bit as difficult, even for experienced birders. A group whose difficulty may not be as fully appreciated as those others until, for example, you find yourself trying to explain what you're looking at for the benefit of those birders following you around and looking for answers.
Shorebird identification alone is hard enough, but in Minnesota and other non-coastal areas its difficulty is compounded, since birders here have comparatively few opportunities to see and study these migrants. We have to rely on temporarily flooded fields in spring, muddy shorelines left by receding lake levels in summer and fall, and the challenges presented by sewage ponds – rip-rapped shorelines where mud ought to be, fences lined with ambiguous no-trespassing signs, and that distinctive fragrance on a hot summer day.
But now is the time to take another look at shorebirds. After all, ever since summer officially arrived in late June, so did the beginnings of fall migration for these birds. And following are some thoughts on shorebird identification that might be worth keeping in mind as you head for your favorite sewage pond.
Also keep in mind that this and all articles in this series are not intended to be complete identification analyses. The points discussed here are only intended to supplement (not replace) your field guides, and to raise some questions you may not have thought of – rather than provide all the answers.
Black-bellied / American Golden-Plovers
As the field guides adequately show, when these two species are in full alternate (breeding) plumage they are not only beautiful to look at but easy to distinguish. And when in flight in any plumage, they are also easily separable. The problem is that Black-bellied Plovers tend to look more brownish as juveniles, and also as adults when they begin to acquire or lose full alternate plumage. Thus, unless they fly, such Black-bellieds strongly resemble golden-plovers.
Try to see the Black-bellied's thicker bill and the relative lack of contrast between the crown and supercilium; golden-plovers tend to have a darker crown which more clearly delineates a whiter supercilium. And, if a juvenile, note its whiter and more contrasting lower belly and undertail coverts (golden-plovers are more uniform below). Unfortunately, unless there is direct comparison between the two, these differences are often difficult to determine.
Also listen for their different calls. The Black-bellied's is mellower, lower-pitched, and usually three-syllabled; the golden-plover sounds screechier, higher-pitched, and one- or two-syllabled. If you're still unsure, wait until it flies, and don't be surprised if your initial guess as to its identity is belied by the field marks on the wings and tail.
Greater / Lesser Yellowlegs
Other than Killdeers, perhaps no other shorebirds are more familiar to Minnesota birders than yellowlegs. But too many birders (myself included) struggle with telling which yellowlegs it is about as often as we see one. When Greaters and Lessers are seen together, the difference in their overall lengths is striking, but otherwise a yellowlegs' size is hard to tell without direct comparison with something else – like a Killdeer, which is essentially the same body length as a Lesser.
Try concentrating on the bills. A Greater's is longer (often appearing twice the length of the head), thicker, usually slightly upturned, and two-toned (gray at the base and blacker on the distal half). A Lesser's bill is shorter (not much more than the length of the head), thinner, straighter, and more uniformly black.
There is another difference on alternate-plumaged yellowlegs, with the Greater being more coarsely barred on the neck, breast, and flanks. Sometimes the time of year is useful, since Greaters tend to arrive earlier in spring and depart later in the fall than Lessers. Also, Lessers tend to linger later into May than Greaters during spring migration and to arrive earlier in July during fall migration.
Many birders tell me they can separate calling yellowlegs by the number of syllables given (one or two for Lesser, three or more for Greater), but I have serious doubts that this is diagnostic. More useful, I think, is the quality of the notes given. To my ear, Greaters sound higher-pitched and more strident than the lower-pitched, mellower Lessers.
Finally, for those with access to back issues of Birding magazine, I recommend the article on yellowlegs identification in the October 1982 issue (14:172-178).
Solitary / Spotted Sandpipers
Because of its overall shape and size, white eye ring, finely spotted upperparts, and vaguely yellowish legs, the Solitary Sandpiper is often mistaken for a Lesser Yellowlegs. Note, however, the Solitary's bolder eye ring, greener legs, and, if visible, its distinctive tail pattern.
Also listen for the Solitary's "peet weet" call note, which sounds a lot like a Spotted Sandpiper: those with a good ear for calls will notice that the Solitary's call is higher-patched than the Spotted's. And this brings up an overlooked identification problem in summer and fall when there are juvenile Spotted Sandpipers around. These have a bold white eye ring, pale-tipped and somewhat spotted feather edges on the upperparts, and dull greenish-yellow legs, and they might be mistaken for Solitarys. Both Spotteds and Solitarys even have similar bobbing body movements. Again, note the Solitary's diagnostic tail pattern in flight, and, if the bird won't fly, note the bill color: dark on a Solitary, pale on a Spotted.
Hudsonian / Marbled Godwits
Godwit identification is similar to the situation with the plovers mentioned above: those in flight and those in full alternate plumage are easily separable, as shown in the field guides. But those godwits in spring that have yet to acquire alternate plumage and refuse to fly present a problem. It is amazing how nondescript they appear and how much the two species look alike, since the Hudsonian is more brownish than rusty below. Unless they call or fly, or unless the Hudsonian's slightly smaller size can be determined by direct comparison with something, the two are quite difficult to separate. And, as with all identification problems presented here, readers' comments on this would be welcome.
One consolation is that godwit identification is not much of a problem during fall migration, since neither species is around here much: Marbleds have generally left the state by the end of July; Hudsonians are only casual in fall, and those here are in basic (winter) plumage, grayish overall, and unlike the browner Marbleds.
Baird's / Buff-breasted Sandpipers
Many birders with limited shorebird experience are surprised during fall migration by how bright and buffy those juvenile Baird's Sandpipers can be: much buffier than shown in any field guide and much like the more sought-after Buff-breasted. In addition, both species often occur in the same habitat – pastures, sod farms, and the like.
But before you call that buffy sandpiper your lifer Buff-breasted, make sure the legs are yellow or even orangish (black on the Baird's), and that the buff coloration extends to the belly or even to the undertail coverts (the Baird's buffiness extends no lower than the breast). Also note that a Buff-breasted's head and face bear a surprising resemblance to a Mourning Dove because of its "beady" black eye on a plain, unmarked face.
Note as well that much has been made in most field guides regarding the Baird's Sandpiper's "scaly" back. While this is certainly present on a juvenile Baird's, it is a highly overrated field mark, since many juvenile shorebirds (Buff-breasted included) have a similar scaly appearance caused by paler feather edges.
Pectoral Sandpiper / Ruff
While most birders are aware how widespread Killdeers and yellowlegs are in Minnesota, many are quite unaware how common the migrant Pectoral Sandpiper can be. It is not at all unusual to find more Pectorals than any other species during a day of shorebirding.
Yet many novice shorebirders have trouble identifying it, probably because it just looks like a nondescript, medium-sized, brown shorebird unless it turns to face you and reveal its diagnostic breast pattern. Even experienced birders are unprepared for how rusty the upperparts can appear on a juvenile, and how much Pectorals vary in overall size: males can be an inch or so larger than females.
Despite its smaller size, black legs, and less heavily streaked breast, a Baird's Sandpiper has an overall resemblance to a Pectoral. A Sharp-tailed Sandpiper has even a closer resemblance, but this would be a first state record (and a subject for another time). Another Pectoral-like species, the Ruff, is also worthy of mention here. Though only listed as Casual on the official Minnesota list, the Ruff has been recorded almost annually in recent years. Juveniles especially look a lot like Pectorals due to their brownish overall plumage and brownish or buffy wash on the breast. Note that this wash is paler and extends lower on the breast than on a Pectoral, and it is not as sharply cut off from the belly.
A Ruff's overall stance may be more yellowlegs-like, but it usually exhibits a distinctive "pot-bellied" and "hump-backed" appearance. Its bill is more like a Pectoral, slightly decurved, relatively short, and pale at the base. Much has been made in the field guides regarding the Ruff's white ovals on the sides of the tail, but be sure to note that Pectorals and several other shorebirds also have white sides on the tail. However, these ovals on a Ruff are larger and nearly meet near the tip of the tail, suggesting a single U-shaped patch.
Stilt Sandpiper / Dowitchers
Everyone knows it's hard enough to tell the two dowitchers apart. But the next time you see what looks like a dowitcher, it might be a good idea to consider whether you're actually looking at a Stilt Sandpiper before getting bogged down in dowitcher ID. Both Stilts and dowitchers have a long bill and pale supercilium, and both characteristically probe the mud with bills held vertically. When not in alternate plumage or when seen at a distance or in bad light, therefore, the two are easily confused.
Like the plovers and godwits discussed earlier, they are readily separated in flight, but otherwise try to see the bill shape: slightly decurved (and shorter, of course) on a Stilt, straight on a dowitcher. Also note that Stilt Sandpipers usually probe less rapidly than dowitchers, and they tend to walk around more than dowitchers as they feed; dowitchers typically stand in one place for longer periods.
Short-billed / Long-billed Dowitchers
In the previous Hindsight article (http://mbwbirds.com/calendar.html), the differences in the migration timing of the two dowitchers and in the plumages of alternate-plumaged individuals were mentioned. A passing reference was also made to their calls: a lower-pitched, mellower, louder, Lesser Yellowlegs-like "tu-tu" or "tu-tu-tu" in Short-billed; a higher-pitched, thinner, softer, "keek" or "keek keek keek" in Long-billed.
During fall migration, both brightly colored juveniles and grayish basic-plumaged dowitchers are also encountered. If a juvenile (an individual with a clean-cut, fresh pattern of rusty feather edges on the upperparts), simply examine its tertials: i.e., the longest visible feathers on the folded wing tips. If patterned with rusty and black markings, it's a Short-billed; the juvenile Long-billed's tertials are unmarked. Note, however, that this field mark does not work on alternate- or basic-plumaged dowitchers. Note as well that those grayish overall basic-plumaged individuals are probably not safely separated unless heard.
My advice on dowitchers is to consult the second edition of the Geographic field guide (the first edition is not nearly as good on this), and remember that the Short-billed subspecies passing through Minnesota is hendersoni. Also for a more thorough, though sometimes confusing, treatment of dowitchers, see the article in the August-October 1983 issue of Birding (15:151-166). [Author's Note, August 2010 – Since 1995, there have been several other identification references on dowitchers, although some are unhelpful and even counter-productive.]
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If you've been able to make your way through this treatise, are you all set to handle the complexities of fall shorebird migration? Hardly. Astute readers should note that nothing here has been said about telling a Semipalmated Sandpiper from a Least or a Sanderling....or a Western. Or, for that matter, how easy it is to confuse a Western with just about everything else, including Leasts, Sanderlings, White-rumpeds, and Dunlins. But this article is certainly long enough already, and these highly confusing smaller shorebirds will have to wait for a future installment in this series.