This article is in 3 parts: Least Peeps | Standard Peeps | Long-winged Peeps

Long-winged Peeps (White-rumped and Baird’s Sandpipers) Figures 14-20

These are the ultimate calidrids with bodies built for their annual round trip journey between the arctic and the tidal flats in the southern cone of South America.  Where numerous, they form large flocks, but many birders encounter them in smaller numbers, mixing with flocks of standard peeps.  Being able to consistently pick these guys out of a large flock of shorebirds is a sign of true peep proficiency.

When standing next to a standard peep, the length of these two species is easily apparent; next to a Least Sandpiper, they are positively hulking.  Unlike the standard peeps, which are similar in their habits, the two long-winged peeps fill slightly different niches.  White-rumped is a habitat generalist, found almost anywhere frequented by peeps, while Baird’s prefers drier habitat: sod farms, moist mud, even dry, short-grass fields.  Baird’s almost always picks from the surface when feeding, even in deep muck or while wading. They often look tentative and uncertain like Least Sandpiper; White-rumpeds feed much like the standard peeps.

Both species have considerably more body projecting behind the legs than in front, and this accentuates their attenuated shape. White-rumpeds tilt forward sharply to reach the ground as they feed, cause the rear to wag up-and-down.  Baird’s may do this as well, but more often they feed in a perfectly horizontal, flat-backed posture.  Both these species have such long wings that their primary tips frequently cross. Often, this is easier to see from a distance than whether the wings project past the tail. The crossed-winged posture is distinctive and instantly places an individual in the “Long-winged” category.  While the primary tips of Western Sandpipers sometimes overlap slightly, this looks nothing like the distinctly crossed sickles of the long-winged peeps.

Baird’s Sandpiper

This species is, primarily, a migrant through the middle of the continent, uncommon to downright rare on either coast, but outnumbering all other peeps combined in much of the Great Plains, particularly in fall.  Baird’s is an earlier migrant than White-rumped, both in spring and fall.  During migration they are sometimes found in small numbers high in the western mountains, feeding in tundra habitat.  Baird’s is the only peep to regularly do so. When feeding, they sometimes take very short steps that move them at a slow steady pace, and create the impression that they are shuffling their feet. This gait seems unique to Baird’s and is quite distinctive. Also more noticeable on Baird’s than other peeps is their tendency to bob their head back and forth while walking.  All peeps do this to some degree, but Baird’s cannot take a step without a corresponding jerk of the head, a behavior reminiscent of Buff-breasted Sandpiper.

Figure 14. click to enlarge Baird's Sandpiper It really does not get any easier than this.  The compressed oval shape of this bird is diagnostic.  Also notice the small head and broad, flat back.  The primaries sticking out on the right side of the bird are from the opposite wing, so the primaries of this Baird’s are crossed.  Neil Loverock Isle of Scilly, UK 09/29

Structure

Like Least Sandpiper, Baird’s has a small head. The bill is fairly short, and unlike that of other peeps, is fine along its entire length. (Fig. 15)  Baird’s has a prominent, rounded eye that gives a permanently frightened appearance.  Unlike other peeps, their bodies have a distinct laterally flattened shape; viewed head on, this is reminiscent of an egg lying on its side. (Fig. 14)  While this shape is not illustrated in any North American field guide, it is shown perfectly in Birds of Europe by Mullarney et al.  Baird’s Sandpipers have short legs, and this, in conjunction with their flattened shape, gives them the impression of hugging the ground.  At times, this can be very striking; enough to quickly pick a Baird’s out of a flock.  Standing next to a standard peep, Baird’s is “wider” but not as “deep”. (Fig. 16) Unlike other peeps, White-rumped and Baird’s have strikingly long primaries extending well past the tail.                       

Figure 15. click to enlarge Baird's Sandpiper Notice how this Baird’s appears to be “hugging” the ground.  It is hunched forward, but the body is still perfectly horizontal.  The tarsi are quite short for a sandpiper of this size.  The eye is striking in the small head and the bill is slender.  The drooped wing is thin and appears saber-like, accentuating the length. Scott Elowitz 09/19/04 Sandy Hook, NJ www.scottelowitzphotography.com

Figure 16. click to enlarge Baird's Sandpiper The oval body shape of Baird’s is virtually always apparent when this species is facing you. The broad, flat back is characteristic of Baird’s.  Note how the head looks small compared to wide body.  This gives Baird’s a broad-shouldered appearance.  The bill is very slender and the crossed primaries trail behind the bird. Cameron Cox Stanwood, WA 27 Aug

Figure 17. click to enlarge Baird's Sandpiper Compare this individual to the White-rumped in fig. 18.  The flattened body shape is evident.  Also note that the eye of this Baird’s really stands out but the head is smaller.  The bill of the Baird’s is slightly finer and straighter.  Both show crossed primaries. Scott Elowitz Sandy Hook, NJ 09/26/2004 www.scottelowitzphotography.com

White-rumped Sandpiper

White-rumped Sandpiper conducts an elliptical migration route, with differing spring and fall routes.  They are late spring migrants through mid-continent North America, while the fall return is primarily over the Atlantic Ocean, taking off from the Canadian Maritimes through New England (though White-rumpeds are fairly common the length of the East Coast in fall).  They are also late fall migrant and juveniles can linger into November.

Figure 18. click to enlarge White-rumped Sandpiper Compare with BASA in fig. 17.  The White-rumped appear more rounded, heavier chested, and slightly more upright than the Baird’s.  The White-rumped appears distinctly larger head than the Baird’s.  Both birds are wading in fairly deep water.  How would each species adjust its feed behavior to this situation?  My hunch is that the Baird’s would pick directly from the surface of the water, while the White-rumped would be more likely plunge it’s head into the water and probe.  Is this true?  Are there other useful differences in behavior in this situation? Scott Elowitz Sandy Hook, NJ 09/25/04 www.scottelowitzphotography.com

Structure

This species is heavy-chested, but appears more balanced than Western Sandpiper because the chest is offset by the long, attenuated body. (Fig. 20)  It usually feeds quickly and aggressively, much like Semipalmated Sandpiper.  In a flock of smaller peeps, White-rumped’s most notable features are the distinctly crossed primaries and the habit of tilting sharply forward as they feed. (Fig. 19) The difference in the angle that probing White-rumps tilt forward compared to standard peeps is almost as dramatic as that of Stilt Sandpiper compared to yellowlegs.  Note that all peeps have a threat posture where the body is tilted forward and the wings drooped.  This could be confused with the tilted stance of White-rumped, but in the threat posture the tail stay up constantly, and is not jerked up and down with the feeding motion of the bird. White-rumpeds have heavier bills than Baird’s and look bulkier and larger headed, with a slightly more upright stance.  (Fig. 18 compare Fig. 17) 

Figure 19. click to enlarge White-rumped Sandpiper Can we be sure this is a White-rumped?  Two aspects of the posture of this bird are immediately apparent.  Even from this angle you can see that the body is tilted sharply forward and the primaries extend beyond the tail with the tips distinctly crossed. This tells us that we are looking at a long-winged peep and strongly suggests White-rumped.  The identification is further supported by the fact that the bill of the bird is buried deeply in the mud.  This not typical habitat or behavior for Baird’s but this should not be considered diagnostic. It this case, the fine streaks along the side clenches the identification as a White-rumped. Cameron Cox 05/08/06 Heislerville, NJ

Flight and Voice

With practice, the long-winged peeps can be picked out of a flock of standard peeps in flight, as their larger size is apparent in close comparison.  The difference in wing structure may be visible, though it is by no means easy to see in a rapidly moving flock. Frozen in a sharp photo, you can see that the wings of the long-winged peeps are more pointed, as the outermost primary (P10) is the longest primary.  In the standard peeps, P9 is marginally the longest primary and the outer three primaries (P8-10) are closer in length so the wing is more rounded.  The wings of the long-winged peeps are narrow and parallel-sided with exceptionally long “hands” that taper gradually.  In the field, it is a feat just to notice that a long-winged peep has longer, slimmer wings than to other peeps.  White-rumped, and possibly Baird’s as well, sometimes perform an extended glide as they land, something the smaller peeps never do.  In a glide, the profile is remarkably similar to a Peregrine Falcon, with the primaries slightly drooped from the wrist and the tip of the wing curled up slightly. 

These species are often heard before they are seen, particularly White-rumped.  Fortunately, both species have distinctive vocalizations.  White-rumpeds call is a sharp, high-pitched “Siit” with an explosive quality.  This call could be confused with Western’s call, but is sharper and more piercing, lacking the whining quality.  White-rumpeds are very vocal, especially in flight, and learning this localization will increase your encounters with this species two- or three-fold. Baird’s is less vocal, but the call is also distinctive once learned.  It gives a descending, trilled “crrep” that is lower-pitched and softer than the calls of other peeps, closest to a soft Pectoral Sandpiper call.

Figure 20. click to enlarge White-rumped Sandpiper Notice the full, powerful chest and large square head.  The bill is slightly heavier than Baird’s Sandpiper.  The long primaries stick out well past the tail.  The heavy chest contributes to a more upright stand compared to Baird’s.  The combination of these features makes White-rumped distinctive from any distance. Steve Mlodinow Barbados

Caveats

Note also that feeding behavior can vary greatly with the surface that birds feed on.  I have tried to describe the most common behaviors, but in certain situations, as when feeding on an uneven surface or in strong wind these behaviors will change. In these situations, all three groups will still feed differently; you just have to discover what the differences are.      

Many of the impressions described here are subject to the perception of the individual observer and may differ from those of the author. However, since these impressions are based on actual differences in structure, they are valid nonetheless.  Armed with the knowledge that these species differ in subtle but consistent ways, each person can form individually tailored impressions of these species.  By combining the characteristics described here with traditional field marks you will have greater success when identifying members of this difficult group.

Acknowledgements:

Many thanks to Ken Brehens and Tony Leukering who both made enormous contributions to the content and clarity of this article.  Charlie Wright also gave me valuable feedback.  Thanks are also due to Scott Elowitz, Nick Kontonicolas, Cin-Ty Lee, Tony Leukering, Steve Mlodinow, and Bill Schomoker for contributing their excellent photographs.  Finally thanks to Cape May Bird Observatory and Dr. David Mizrahi for hiring me to do shorebird surveys and to the entire Cape May birding community for all they taught me.