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Tucson Audubon Society
Dastardly Duos
Western
and Least Sandpipers
by Larry Liese
Illustrations by George C. West
(Reprinted from the April, 2002 issue of
the Vermilion Flycatcher newsletter. To receive the newsletter in
the mail, become a member of the Friends of
Tucson Audubon.)
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Spring is here! This time of year is when shorebirds are migrating through, and two shorebirds that confuse some of us regularly are Western and Least Sandpipers. Although the books say that these two are easy to identify (if Semipalmated Sandpipers are not in the area), they are very similar in appearance at longish distances or under poor lighting conditions. Least Sandpipers can be encountered in southeastern Arizona all months except late May through June, while Western Sandpipers are common only around April and August/September.
The key to becoming confident in identifying these two species is to observe them when they are present together, seeing how their differences appear to you. Recently, I encountered a single Western amongst several Least Sandpipers at close range. I was astonished at how different they appeared!
Most birders are aware that Western Sandpipers have black legs and Least Sandpipers have yellowish ones. This works great at close range but can be frustrating when a low sun angle causes lots of shine from wet mud or water, or when Least Sandpipers have muddy legs! A bright sunny day is surprisingly not the key, as I found out on one outing. The legs of a Least Sandpiper appeared dark in the shade of its body and only showed the light color when illuminated directly by the sun, so be careful with leg color.
The lesser known but distinct other differences are in body and bill shape, upper breast streaking, back/scapular coloring, and overall color. From long distances, a Least Sandpiper’s shape will look plumper and more compact. Western Sandpipers have a lankier look. Western Sandpipers in general have a longer bill which droops more than the Least Sandpipers do. The Western’s bill is broader based and narrows conspicuously.
Plumages vary considerably with age and season, but some traits hold for the times they are common here. Least Sandpipers are browner with more streaking on the breast, while Westerns are grayer, have a “salt and pepper” look, and have more white in the throat and upper breast. Western juveniles and adults entering breeding plumage have rufous feathering on the scapulars (auriculars and crown on adults as well). This coloring contrasts highly and can be easily distinguished from the overall brownish color of the Leasts. A Least Sandpiper’s head and back will appear the same color, while a Western Sandpiper typically has a contrasting cap color.
Try observing posture and habits once you’ve identified a mixed group. I haven’t seen this yet, but the Least is supposed to look more crouched and the Western more long-legged and front-heavy. I’ve also heard that when both are present in numbers one of them likes slightly deeper water than the other, but I forget which!
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This page was updated on 02/21/06