BIRDING BY HINDSIGHT: A Second Look at Western (and Eastern) Sandpipers

In a previous Hindsight article on shorebirds (http://mbwbirds.com/shorebirds.html), the author, wisely choosing discretion over valor, temporarily managed to avoid the subject of “peeps”. This group of the smallest shorebirds, which includes Least, Semipalmated, Western, Baird’s, and White-rumped Sandpipers (some birders would also include a few other species within the genus Calidris), generally gives shorebirders the most headaches.

This need not be the case, however, since there are plenty of other shorebirds out there which can also be a pain to identify. In other words, shorebirds may be among the most difficult birds for beginners, but, if the birder has learned to figure out at least some of those yellowlegs and dowitchers, telling the peeps apart is really no more difficult.

As with other articles in this identification series, there is no need for this piece to repeat information found in the standard field guides. And, at the same time, a complete analysis of complex identification points would be beyond the space limitations of this journal and the patience of its readers. With this in mind, there are really only six essential points to remember when trying to identify peeps — especially the notorious and mythical Western Sandpiper:

1) First and above all, put aside the field guides (Geographic included) and get a hold of a copy of “Field Identification of the Smaller Sandpipers Within the Genus Calidris”  by Richard Veit and Lars Jonsson, which appeared in the September–October 1984 issue of American Birds (38:853–876). The article is so good it was reprinted three years later in the same journal (41:212–236), and it is about the best identification article on any group of birds I have ever seen.

While it does not include the Baird’s and White-rumped Sandpipers, it is no exaggeration to say that if you have this article there may be no need to read the rest of this piece or any other book or article on Leasts, Semis, and Westerns. (But if you’d like some further reading on the peeps, I would certainly also recommend Shorebirds: An Identification Guide by Hayman, Marchant and Prater, and Dennis Paulson’s book Shorebirds of the Pacific Northwest.) [Author's Note, July 2016 –  More recent and recommended shorebird references are The Shorebird Guide by O'Brien, Crossley, and Karlson, and Shorebirds of North America by Paulson.]  

2) Keep in mind that plumages vary with age and the time of year. For example, an adult Least Sandpiper in spring might look plain brown overall and unlike a fresh-plumaged and somewhat rusty juvenile Least in fall.

3) There are more important things to study than leg color. The non-black legs of a Least might appear to be quite dark if the bird is in unfavorable light, at a distance, or wading in mud. A Least’s plumage or bill shape is usually more evident and useful than its leg color, and, besides, there is no difference in the leg color of the other four peeps.

4) If the bill on the peep you’re studying appears to be somewhat decurved, you unfortunately haven’t narrowed down its identity — and it certainly is not necessarily a Western. Individual peeps of any of the five species can have decurved bills: in fact, with the exception of most Semipalmateds, almost every peep you study (including some Semis) will have a slightly decurved bill!

5) If the plumage of the peep you’re studying appears to be somewhat rusty, you unfortunately haven’t narrowed down its identity — and it certainly is not necessarily a Western (sound familiar?). While a Baird’s would be more accurately described as buffy, individuals of all the other four peeps, especially when in juvenile plumage, often have some rusty feather edges on the upperparts.

6) And finally: yes, Virginia, there may be a Santa Claus, but, contrary to popular belief, there is no Western Sandpiper on Minnesota’s regular list. In fact, there is currently only one specimen record in the state (which might need to be reexamined?), no photographs (although some may exist of a probable Western in Duluth in May of this year), and only two documented sight records (with a third pending) which have been accepted by the Records Committee. [Author's Note, August 2010 – A few additional records of this now-Casual species have now been accepted.]

Yes, there have indeed been several peeps identified as Western Sandpipers over the years in Minnesota — and some of them were my records before I read that 1984 article. And, yes, the species continues to be reported on a regular basis in neighboring states. But I strongly suspect the majority of these sightings, perhaps virtually all of them, both those in former years in Minnesota and the ones still reported nearby, are erroneous.

So much for some basic essentials. Now for some idle ramblings on each of the five peeps, especially that Western Sandpiper, plus some thoughts on two potential Western look-alikes: the Sanderling and Dunlin. Again, what follows is not intended to be a thorough analysis. Rather, these comments are only intended to help the reader to start noticing the more useful field marks and to be aware of those features which may lead to misidentifications.

Least Sandpiper

You have spotted a peep with a slightly but definitely decurved bill, extensive rusty coloration on the upperparts, and what appear to be dark legs. A Western, right? No, a Least would be far more likely. A finely tipped and slightly but noticeably decurved bill is entirely normal for this species. Couple this with the extensive and generally uniform rusty coloration of its upperparts (a feature of juveniles especially), and its easy to see why a Least — when its legs are muddy or hard to see — is often mistaken for a Western.

Note that Leasts in both alternate (i.e., breeding) and juvenile plumages usually appear darker on the breast and browner or more reddish-brown on the upperparts than either the grayer Semi or Western. Also note the color of the upperparts on a Least is more uniform and extensive. When rustiness is present on a Semi or Western it tends to be limited to certain areas — especially on the scapulars, but also sometimes on the head, back, and tertials.

While a Least is slightly smaller than either a Semi or Western, this difference would probably be noticed only if direct comparison were available. Just as useful is the Least’s call note: a high-pitched “crreeep”, which is similar in quality to the lower-pitched note of the Baird’s.

Semipalmated Sandpiper

Now you see a peep with a bit of downcurve towards the tip of the bill, some definite rusty edges on the back, scapulars and tertials, and black legs. A Western, right? Probably not: a Semipalmated would be far more likely. Unfortunately some Semis (probably adult females) can have a bill which is every bit as long as on some shorter-billed Westerns (probably juvenile males).

Equally as troublesome is that many Semis in alternate and juvenal plumages have rusty feathers on the head, back, scapulars and/or tertials — a feature generally thought to occur only on Westerns until that 1984 American Birds article. But a dozen years later such Semis are still routinely misidentified as Westerns. If the bird in question is an adult, try to see if the rusty coloration is on the feather edges (indicating a Semi) or on the bases or centers of the scapular feathers (indicating a Western).

If, however, that rusty bird is a juvenile, the identification becomes more difficult. But the rusty feather edges on Semis may look duller, the color more extensive and not as sharply delineated from the grayer wing coverts, and its back might have a scalier look than on a Western.

Without direct comparison, there is usually no noticeable difference in overall size between Semis and Westerns, but of possible use is the difference in their call notes: the Semipalmated gives a nondescript “chut” or “churp”, while the Western has a thin, White-rumped-like “jit” note.

Western Sandpiper

I think it was someone named Horace Greeley who said, “Go West, young man.” Sound advice, perhaps, in the 1800s, but today it’s almost always the wrong direction to go when identifying shorebirds in Minnesota. As mentioned elsewhere in this article, there are only a few documented records in the state, along with a long history of other things misidentified as Westerns. The sections on Least, Semipalmated and White-rumped sandpipers, Sanderling and Dunlin discuss the reasons why these other species are mistaken for Westerns.

A Western in full alternate plumage should be distinctive enough, as long as the possibility of the somewhat similar White-rumped is considered and precluded. During fall migration, the correct identification of a juvenile or molting adult Western would probably require careful study, complete field notes or photos, and consultation with sources other than the standard field guides. And while a generally grayish peep in basic (i.e., winter) plumage in Minnesota would not be a Semipalmated (which would not molt into basic plumage until much farther south) and might actually be a Western, the more likely possibility of Sanderling must be considered.

Baird’s Sandpiper

Here, at least, is one peep not likely to be confused with a Western. In both alternate and juvenal plumages, the overall buffiness of this peep’s plumage — especially in juveniles and especially on the breast — bear more of a resemblance to a Pectoral or even a Buff-breasted. But given a decent view, the underparts patterns on Pectorals and Buff-breasteds differ from Baird’s, as do their leg colors. Along with the White-rumped, the Baird’s is larger than the other three peeps, and its folded wing tips extend beyond the tail, giving this peep’s silhouette a distinctively long and pointed look posteriorly. Listen also for its call: a rolling “crrreep”, similar in quality to the Least and Pectoral and in between those two in pitch.

Two caveats. First, the field guides are fond of mentioning the scaly appearance of this species’ back, even though such scaliness is typical of many shorebirds in juvenile plumage. And second, when trying to identify a Baird’s, beware of the illustrations in the shorebirds guide by Hayman et al., which to my eye fail to accurately portray what a Baird’s looks like.

White-rumped Sandpiper

When the rump of this species is seen in flight, it is certainly distinctive. At rest, however, it poses a definite source of confusion with the Western Sandpiper unless the White-rumped’s larger size and wing tips extension beyond the tail are noted. Both White-rumpeds and Westerns in both alternate and juvenile plumages have several features in common: a slightly decurved bill (note the White-rumped’s bill is usually paler at the base, unlike other peeps); a clearly delineated set of rusty scapulars; a distinctive set of fine streaks or rows of spots across the breast; and even the same thin, flinty “jit” call note.

In addition, just like a Western, an alternate-plumaged White-rumped also has a rusty crown and ear coverts. It is also worth noting that White-rumpeds are generally seen in Minnesota only in spring migration. In fall they are only casual or rare, although they are still more likely then than a Western.

Sanderling

When in basic plumage, this is potentially another species which resembles a Western. Although the Sanderling is larger, with a straighter bill and a bolder wing stripe, its pale gray overall plumage looks a lot like that of a basic-plumaged Western.

Dunlin

Though the Dunlin is also larger than a Western Sandpiper and its plumage is darker gray overall, when in juvenile plumage it might be confused with a Western. This is due to its clearly drooping bill, its rusty-edged scapulars, and its finely streaked or spotted underparts.

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One final thought. If the hints expressed here have been helpful, and you now have the confidence to look at a peep without awe and fear, I have some good news, some bad news, and some more good news. The good news is you are well on your way to being able to manage one of the most difficult bird groups of them all. The bad news is there is still another group of shorebirds even more complicated – a group so challenging that the additional good news is I won’t even think about writing an article about them.

But be aware of the existence of those four small Eurasian shorebirds known as stints: i.e., the Red-necked, Little, Temminck’s, and Long-toed. Although there are no records of stints in or near Minnesota, some of them could occur here — and perhaps already have — but be easily overlooked or misidentified as something else. For more information about this group, be sure to consult the American Birds article mentioned earlier in this article.