Clark's
Grebe, Aechmophorus clarkii
Clark's and Western Grebe were long considered two forms of the same species and only recently recognized as separate. The picture below shows birds of both species together, the Clark's behind, and illustrates the standard distinguishing marks: Clark's has an orange rather than a greenish bill, lighter flanks, and the dark crown ends above the eye.
Both Clark's and Western Grebes normally nest in large colonies on freshwater lakes in the interior of western North America. A single pair of Clark's surprised local birders in 2011 by nesting on a small nearshore island in Salt Pond A1 in Mountain View, bordering on southern San Francisco Bay. Below are the pair together, with a newly hatched chick riding on the back of one of the adults; above is the other adult incubating the remaining unhatched egg on the nest. In this species both sexes incubate equally, but while both adults of both sexes carry the new chick ("back-brood") in the fashion shown below, the male does so more frequently. The adult back-brooding the chick in this picture was noticeably larger than the other one, with a longer bill and a larger crest, and observers generally called it the male of the pair, but there do not seem to be any predictable sex differences in size or plumage in this species. Sadly, the nesting effort failed; the single chick shown below died shortly after this picture was taken, and no other chick was observed.
