Image: John del Rio [larger view].
Please name at least one field mark that supports your identification.
Rick Wright, Managing Director of WINGS Birding Tours Worldwide, writes:
You probably don’t know that these photos are usually sent to me without the “answer.” But like most of you, I knew right away what this worth-two-in-the-bush nub of stringy fluff was; or did I? It was easy enough to rule out the plain, almost duckling-patterned Aechmophorus grebes, but as I pondered, it occurred to me that I’d never really had close looks at any other grebelings but Pied-billeds, and there was a bit of a logical short-circuit in my quick step from “grebe” to “Pied-billed Grebe.” The fact that my identification turns out to be accurate doesn’t make up for the fact that I made it without a fair consideration of all the other little grebes (oops, better make that small grebes) of the world.
How did we all know it was a grebe? The intricately striped pattern of the filamentous down is a good start. The short, bluntly pointed bill (already with a ring around it, by the way) also rules out other groups of waterbirds.
From here, if we start from the virtuous position of assumed ignorance, it gets a little tougher. I don’t have access to specimens or photos of all the downy grebettes of the world, but since this mystery bird was photographed in California, maybe I can be excused for limiting the possibilities right away to the species that breed in western North America. Clark’s and Western Grebes are much bigger than this when they hatch, and their down is whitish or gray, paler in Clark’s. Downy Podiceps — for our Californian purposes, Red-necked, Eared, and Horned Grebes — are said to lack stripes on the back. We’re left with Pied-billed and, I suppose, Least Grebe, chicks of which are both striped with variable density on the sides of the head. Apparently, among New World grebes north of Central America, only Pied-billed Grebe shows the rich rufous down at the side of the nape and on the lore and eyeline; this species also lacks the bare crown patch shown by many other grebe chicks.
So I know more tonight than I did this morning, always the sign of a good day’s birding.
Review all mystery birds to date.