I have White-rumped Sandpipers flagged as “rare” in eBird in the counties I review because they’re a scarce migrant that is often mis-identified. I cringe every time I get a report that relies most heavily on “I saw the white rump in flight”. Not to say that you can’t see the rump on a bird in flight, but it’s very difficult to see it unless you’re close, the bird isn’t flying erratically (Iike small shorebirds tend to do), you have excellent optics, great light, and hell – just a keen eye. I’ve seen many hundreds of White-rumped Sandpipers and I can’t honestly remember a time that I identified one in flight. That isn’t to say it can’t be done, but it’s tricky and there are much better ways to identify this species.
This year, I’ve gotten a little better with my photography skills and have taken a million pictures of White-rumped Sandpipers that I’ve found in three locations in Duval County thus far (Spoonbill Pond, Haulover Creek, and Heritage River Road Wetlands). I hope that these pictures and explanations are helpful study guides for anyone struggling with identifying these birds in the field.
Tip 1: I start looking for White-rumped Sandpipers in northeast Florida after the first of May, and then by scanning flocks of shorebirds in shallow pools and mudflats. This could mean inland puddles in flooded fields or pastures, places like Spoonbill Pond, or tidal marshes with exposed mud. A quick scan of a flock of small birds should tell you right away if a White-rumped is present, because they are significantly, noticeably larger than Least and Semipalmated/Western Sandpipers. Figure 1 below may be a typical binocular view of such a flock; you can see how easily the larger White-rumped stands out from the Semipalmated and Least Sandpipers.
Figure 2 below shows the significant size difference between a White-rumped and Least Sandpiper.
Tip 2: Look for the reddish area at the base of the lower mandible. This is actually easier to see than it sounds. Figures 3 and 4 illustrate just how easily that field mark stands out.
Tip 3: The classic profile. To me, White-rumped Sandpipers have a classic profile that is often described as “long”, “lean”, or “attenuated”. Figure 4 above illustrates this look to a tee. In that image, not only can you see the red area at the base of the mandible but you can see that tapered look where the strong muscular back dips to a narrow point around the rump before flaring out through the length of those long primaries. The primaries and tail often present a “scissored” look like you see in Fig 4. Another view you may see is from the front or rear of the bird, where the “scissored” effect is even more dramatic, as in Fig. 5. This bird was photographed in May 2016 at Westside Industrial Park and you can clearly see how the primaries are so long that they cross in the back. When you see this, you have one of two things here: White-rumped or the incredibly more rare Baird’s.
Tip 4: The supercilium. The White-rumped Sandpiper will display a white supercilium in all ages and plumages. Figure 4 demonstrates this as does Figure 6, where you can’t even see most of the bird’s face and none of the bill.
Tip 5: The rump. The most common eBird comment made when writing up this species is something about “seeing the white rump in flight”. It should be noted that Western, Least, and Semipalmated Sandpipers all also have white in the rump, as do Sanderlings, Pectorals, Dunlin, and Stilt Sandpipers! What I don’t recall ever seeing is anyone extending their comment to specify the White-rumped Sandpiper has a solid, unbroken band of white in sort of a horseshoe shape (Fig. 7) and stating that the bird they saw had this trait and not a broken pattern divided by a dark central point like some of the other species mentioned would exhibit. I can’t stress this enough: use caution when relying on seeing a flash of white in the tail or rump of a shorebird to ID it to species.