ID Challenge: Hint -- It's a Waterbird

Often in birding, one comes across a familiar bird in an unfamiliar plumage. At first glance, a common bird in an aberrant or transitional plumage can fool even the experienced observer into thinking they are onto something really rare. In most cases, further study readily reveals that the bird is something expected rather than a first state record. I recently came across just such a bird. Among several pictures I took, I found the image below and immediately recognized that it might present a fun ID challenge. We'll give our readers a few days to try their hand at pinning a name on this bird before sharing its identity. Good Luck.

This bird was photographed in the U.S. (Lower 48) on 22 May 2010. Photo by Dave Irons