How many bird species are in this photo?
OK, here here we have a fairly typical situation when shorebirding; a mixed species flock with plenty of birds to sort through. Having more birds in view helps in the identification process because we can compare any unknown species to the ones that we do know. Perhaps the best way to start is to find the most obvious species. In this group, that would probably be the gaudily marked bird with the bright orange legs left of center. This is a Ruddy Turnstone. Six birds in this group have a single dark band across the breast, uniform brown back, light orange or fleshy legs, a short yellow bill, and they are smaller than the Ruddy Turnstone. These are Semi-palmated Plovers. That leaves two more species. One species (six birds) is larger than the Ruddy Turnstones, with drab gray breast and uppersides, yellowish-green legs, and a mid-sized bill. Birds with drab plumage can give many birders problems, but the structure and size relative to the Turnstones narrow the possibilities significantly. These are Red Knots in non-breeding plumage. The final species (three birds) is intermediate in size between the Turnstones and Semi-palmated Plovers, and is undergoing molt, but with the most striking feature being their overall brightness and relatively short fine bill. These are Sanderlings. Note how some of these birds would be much more difficult to identify without the Ruddy Turnstones as a size comparison.
The lesson here: use size when trying to ID shorebirds. From the Sibley Field Guide, here are the sizes of the shorebirds in this photo:
Semi-palmated Plover 7.25″
Ruddy Turnstone 9.5″
Red Knot 10.5″
Doesn’t that make it easier, instead of relying completely on plumage colors and patterns?