Adapted from Jim Conrad's online book A Birding Trip through Mexico, This excerpt from "The Gulf-Coast Beach at Montepio" in southern coastal Veracruz state
BLACK-BELLIED PLOVER
On my first beach walk I spot a medium-size, moderately long-legged bird with a slender but relatively short beak, probably some kind of plover. However its plumage is splotchy and unlike anything illustrated in my field guides.

This little mystery is exactly the kind of bird-puzzle that pleases me. From a distance with my binoculars I absorb as much as I can of its size, shape, color and behavior, then thumb through the field guide seeing what the possibilities are for this part of Mexico during this time of year, and there are several. I suspect it's a Black-bellied Plover with a plumage changing from its striking summer costume to its duller winter one. However, this bird isn't showing the fieldmarks needed for a solid identification.

Once my mind is clear on which identities are possible, and which fieldmarks characterize each species, with my binoculars raised ready to be looked through in an instant, I purposefully walk toward the mystery bird. It flies up, the binoculars are in place, and I see very clearly a white rump and black patches beneath the wing. It is indeed the Black-bellied Plover, a bird I seldom see.

One reason I seldom see it is that it nests only in the arctic tundra, and winters only along the coasts, and I just miss it during migrations.

I'd like to see this bird in its full summer plumage. Most multi-hued birds are dark above and pale below -- a scheme known as countershading. Countershading helps camouflage a bird. During the summer, Black-bellied Plovers are black below and much paler above -- examples of "reverse countershading," which makes them more visible. Black-bellied Plovers and Bobolinks are among the best examples of reverse countershading, and I just wonder what adaptive pressure encouraged these species to evolve in a direction opposite to most other birds.