Like other curlews, the decurved bill is used to probe in the mud for invertebrates. The Whimbrel is said to be a specialist on Fiddler Crabs. Their bill decurvature matches the burrow curve of these crabs.
They are a fairly common migrant and winter visitor along the California coast. They tend to avoid the interior, but I have seen flocks feeding on grasshoppers in coastal farm fields. Otherwise I usually find them on beaches and rocky shores. They are long-distance migrants with a portion of their population wintering along the coasts of South America.
Prior to 1957, the North American populations were considered a separate species from Old World forms. It was called the "Hudsonian Curlew," and differs from Palearctic races in having a dark rump.
As in the other shorebirds in this series, I believe this is an adult molting into winter plumage. However there is little difference between breeding (alternate) and winter (basic) plumage in the Whimbrel so transitional birds show much less obvious patchiness. The pink base to the mandible is a non-breeding feature. The relatively long bill suggests the bird is an adult.
Digiscoped with Panasonic DMC-LZ5 | Nikon FieldScope 3 | 30X WA | hand-held (no adapter)