Mystery Bird: Semipalmated plover, Charadrius semipalmatus

tags: Semipalmated plover, Charadrius semipalmatus, birds, nature, Image of the Day

Read a beautifully written and detailed analysis supporting the ID of this species below ..

Rick Wright, Managing Director of WINGS Birding Tours Worldwide, writes:

We birders love the technical terms of our trade, delighting sometimes overmuch in tarsi, tomia, and terts. But it can be equally productive, and far more instructive, to step back once in a while and avail ourselves of a less specialized vocabulary. What's the first word that springs to your mind when you see the bird in the quiz photo?

For me, it's "cute." This is a pudgy little bird with a round head and a snub "nose," a combination of shapes and aspects that brings out the nurturer in adult humans. "Aww," we say, "look at that sweet little plover!" No sandpiper is ever this cuddly-looking.

The bold plumage markings of this bird place it within the genus Charadrius, the so-called ringed plovers. Once we've got that far, it's fairly easy to narrow the possibilities using first coarse impressions. The bird's short rear end rules out Killdeer immediately. And it's dark-backed, to be sure, a feature often harped on to distinguish the "wet-mud" species from their "dry-sand" cousins; but more useful at any distance is the face: is this bird dark-faced or pale-faced?

Note that we're not concerned (yet) with the precise details of the face pattern, only with the overall impression it makes. To my eye, this bird is nearly helmeted. Snowy, Piping, and Wilson's Plover all show much paler faces, the pattern obviously black-on-white rather than this bird's white-on-black. That leaves us with only one real possibility, the abundant (and enormously cute) Semipalmated Plover.

There's a complication, of course, and that is the fact that shorebirds are so prone to occur outside of their "normal" range. It's perfectly sensible to rely on probability and range in identifying this Texas bird as a Semipalmated Plover -- but for the sake of thoroughness, just what keeps this bird from being that ornithologically blessed state's first Common Ringed Plover? I don't know that species well enough to blah on about its structure and shape, but I do know the details of face pattern that let us identify this one definitively as Semipalmated. Note first that the quiz bird shows very little white behind the eye; one would expect a conspicuous slash on a Common Ringed Plover. The shape of the white forehead patch is also inconsistent with Common Ringed: on that species, the angle of the white in front of the eye tends to be obtuse, while on Semipalmated (as here) the white patch ends in an acute point. Most critically, look at the dark line connecting the "cheek" to the base of the bill. It narrows distally, such that the dark feathering meets the bill on only the upper mandible; on Common Ringed, the entire base of the bill touches black feathers.

Many of you will have aged and sexed this bird, too. The badly worn, almost shredded wing coverts make it an adult (juveniles are fresh and tidy as can be this time of year), and the lack of glossy black on the head suggests that it is a female.

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