Under the Radar: Field ID of the Solitary Sandpiper

This succinct and informative analysis is an installment in the “Featured Photo” column appearing in each issue of Birding.

In Brief

Fig. 1 • Featured Photo—Solitary Sandpiper. Although in different genera, Solitary and Spotted sandpipers are frequently confused. The relatively dark upperparts, highlighted by a variable number of white or buff spots, enable rapid discernment of the Solitary Sandpiper from the Spotted Sandpiper. Licking Co., Ohio; May 4, 2020. Photo by © Brad Imhoff.

Shorebirds cause identification difficulties for many birders. Based on my extensive experience reviewing eBird photos, the Solitary Sandpiper ranks high among those species that are most confusing, despite its numerous distinguishing features. The Spotted Sandpiper is the species most frequently misidentified as the Solitary Sandpiper, even though the two species are in different genera. The reverse is also true, but at a much lower frequency. The two yellowlegs species, particularly the Lesser Yellowlegs, are the only other species that are often mistaken for the Solitary Sandpiper in eBird photos. This article, then, focuses on differentiating the Solitary Sandpiper from the Spotted Sandpiper, Greater Yellowlegs, and Lesser Yellowlegs. I use the informal but useful term “wing feathers” to include the upperside wing coverts (particularly the greater secondary coverts), the scapulars, and the tertials, but not

Solitary Sandpiper vs. Spotted Sandpiper

A mantra I find useful: If your bird has bars on the wing feathers, it is not a Solitary Sandpiper. If your bird has spots on the wing feathers, it is not a Spotted Sandpiper.

An adult Spotted in breeding plumage, with many large, blackish spots scattered across its white underparts, is not readily confused with a Solitary. However, juvenile Spotteds and adults with few or no black spots below create confusion, and so I concentrate here on the differences between the two species in fall and winter.

If the bird’s dark upperparts coloration does not do it for you, the markings on a Solitary’s wing feathers should. Critical in this vein is that wing markings are not just random or interchangeable across species; on many species, they provide excellent identification clues. In the case of Spotted vs. Solitary, the wing-covert markings—usually discernible, even at a distance—are sufficient for the ID.

The relatively dark wings of a Solitary have, to varying degrees, pale spots that contrast strongly with the dark ground color of the wing feathers (Fig. 1). These spots may be white or buffy, a point we shall return to. The upperwing coverts of the Solitary exhibit some ill-defined and amorphous darker markings, but they do not stand out on the dark brown wings; thus, the pale markings are the stars of the show. The overall impression is of dark wings seemingly randomly accented by small, contrastingly pale spots.

The Spotted’s wing feathers lack pale spots. Instead, they have dark bars that are typically blackish, contrasting more strongly with the paler ground color than do the dark markings on Solitary’s wing feathers. Additionally, those dark bars are bordered above and below by paler bars, which may be off-white, buff, or nearly orange (Fig. 2).

As long as you are looking at the bird’s wings, check the bird’s primary projection, defined as the length that the blackish primaries protrude beyond the brown tertials. Solitary has a long primary projection, such that the tail is frequently not visible on standing birds (Fig. 3), whereas the primaries of Spotted project barely, if at all, beyond the tertial tips and do not reach the tail tip (Fig. 2).

On a flying Solitary Sandpiper, the wings are extensively dark, both above and below (Fig. 4), with the wing linings heavily barred blackish. Conversely, Spotted Sandpiper sports an obvious, wide, white wing stripe, visible both from above and below, and the inner portions of the undersides of the wings are white.

Other useful characteristics involve the tail. Spotted has a fairly nondescript white-rimmed brown tail (Fig. 5a). The tail of Solitary is striking: Most tail feathers are white with broad black bars, but the two innermost tail feathers typically are contrastingly dark (Fig. 5b). The flight style of the Spotted is highly distinctive: buzzy and low over the water, with almost quivering wingbeats. However, the Spotted’s long-distance traveling flight is very different.

Solitary Sandpiper vs. Lesser Yellowlegs and Greater Yellowlegs

In reviewing photos submitted with eBird checklists over the years, I have found that neither yellowlegs species is confused with Solitary as often as is Spotted—even though Solitary and the two yellowlegs species are in the same genus. However, both Lesser Yellowlegs and, less frequently, Greater Yellowlegs create confusion with Solitary at times.

The bills of Solitary Sandpiper and Greater Yellowlegs can be surprisingly similar, with both having an extensive yellowish base that causes the dark nostrils to stand out in strong contrast, providing a feature for a quick-and-dirty distinction between Lesser Yellowlegs and both Solitary Sandpiper and Greater Yellowlegs. While a small percentage of Lessers have a bill base pale enough to contrast with the nostrils, that color is only very rarely yellow; and when it is, that yellow is much more restricted in extent, generally not reaching the nostrils from the gape.

Bill shape and length also provide clues among these three Tringa species. The Solitary Sandpiper has a thick base to the bill, relative to that of Lesser, and many Solitaries have a bill tip that droops subtly. In both yellowlegs species, the bill only very rarely droops at the tip. Beware, however, that short-billed Greaters are not infrequently mistaken for Lessers; the basal coloration of the bill can help in getting that identification correct. An upturned bill tip—slightly or more so—among these three Tringa is definitive for Greater.

Because the wing-feather markings of these three Tringa species are roughly similar (and quite unlike those of Spotted), this feature can lead to confusion and misidentification. The plumage of the Solitary Sandpiper is darker overall than that of either yellowlegs, causing the pale markings on its wings to contrast more strongly, especially in comparison to Greater Yellowlegs. As noted above, the pale markings on the wing feathers of a Solitary Sandpiper tend to be round, at least roughly, whereas those on the wings of the two yellowlegs can be of a variety of shapes: bars, triangles, butterflies, squares, trapezoids, and rhombuses, often with multiple shapes on a single individual; see Figs. 6a & 6b. Conversely, the dark markings on the wings of either yellowlegs are more pronounced than those on the wings of a Solitary Sandpiper due to their greater contrast with the background color; this is particularly true on Greater Yellowlegs.

On flying individuals, the color and pattern of the tail and the presence or absence of white spotting on the secondaries are useful. The tails of all three species are mostly white but with many bands of dark bars, with the number of bands corresponding to the relative sizes of these sandpipers. The smallest species, Solitary Sandpiper, has four or five bands (Fig. 5a); the largest, Greater Yellowlegs, can have 10+ (Fig. 7a); and the intermediate species, Lesser Yellowlegs, has around eight (Fig. 7b). The bands on a Solitary’s tail are darker and much more distinct than those on either yellowlegs. On the two yellowlegs species, the tail bands become obviously weaker toward the base, but on Solitary, the bands are of nearly equal width and darkness throughout. The tails of Greater have a strong tendency for the central tail feathers to be extensively dusky for the distal half or more, but the central rectrices on Solitary are typically wholly brown except for small-to medium-size whitish or white spots that align with the white bands on the tail. Finally, the outer webs of the secondaries and inner primaries of Greater Yellowlegs (Fig. 7a) have small spots of both white and black, whereas those feathers on the other two species are unmarked (Fig. 7b).

Solitary Sandpiper Subspecies

The two subspecies of the Solitary Sandpiper are frequently denoted as “Eastern” (nominate solitaria) and “Western” (cinnamomea) breeders. Nominate solitaria breeds east of the Rocky Mountains south to about 50° latitude from southeastern British Columbia east to Labrador, whereas cinnamomea breeds north of 60° latitude from central Alaska and the Northwest Territories south to northern British Columbia and northeastern Manitoba; see the overview in William Moskoff’s Birds of the World account. Those ranges affirm the names “Eastern” and “Western,” but “Southern” and “Northern,” respectively, might be just as apt. Western cinnamomea is scarce but regular on migration in the western portions of the mainland ABA Area, but is likely much less so in the east. More study is needed!

During spring, the two are difficult to distinguish under most field conditions, with nominate solitaria being darker above with blackish lores, while cinnamomea is browner above and has brown lores. However, juveniles of the two subspecies, widely noted at mid-latitudes in the ABA Area from July into early winter, are readily distinguished in good light at reasonably close range. The spotting on the upperparts is white on nominate solitaria; on cinnamomea, the spotting is brown, pale buff, orange-buff, or cinnamon (whence the subspecific epithet).

Accurately assessing color in the field, especially when we are dealing with earth tones, is fraught. The best method is to compare the color of the spots with that of the white flanks. On nominate solitaria, the white spots should appear the same color as the white flanks; on cinnamomea, in contrast, the cinnamon (etc.) spots contrast with the white flanks (Fig. 3). As to the Featured Photo itself (Fig. 1), the bird is likely referable to nominate solitaria simply by range; however, the photo is from May, and, as noted above, the bird probably cannot be safely assigned to subspecies by plumage alone.

In Sum

First, make sure a prospective Solitary Sandpiper isn’t “just” a Spotted Sandpiper! Next, consider the two yellowlegs species, especially Lesser Yellowlegs. Finally, for an extra ID challenge, try separating the two subspecies: Juveniles, widely noted from mid-summer well into the fall and even early winter, are the individuals most reliably identified in the field.

Acknowledgments

I greatly appreciate the review of a draft of this article by Steve Mlodinow, Kathy Mihm Dunning, and Linda Chittum.