Anna's Hummingbird - Calypte anna

We may not have a great variety of hummingbirds, but we do have an abundance of Anna's Hummingbirds, a species that has flourished and extended its range as homeowners install feeders and plant ornamental flowers.

Anna's are present year round in our Mediterranean climate, although some probably still migrate. The males are territorial and love to sit on an open perch to display their gorget, probably more to warn other males than to impress a female, who accepts him for mating only if he impresses with her with an aerial  diving display. Here he is sitting and giving me a look-over. The rose iridescence varies with the angle of the light, and often is seen on the crown as well. Note the pollen on the bill tip.

Here's one with the crown lit up:

A shot from April 2008 at Mt. Burdell shows how the color can vary, in this case a pretty violet:

I watched this Albany male for about 5 minutes as he sallied out to catch small insects, returning to his favorite open perches. As he lands the tail is spread and the wings fold, slow enough for the camera to capture some detail in the 10 primaries (outer flight feathers), 6 secondaries (inner wing), and 10 rectricies (tail feathers).

Another shot of the same bird landing on a different perch. Note that the tail feathers of the male are pretty much all shades of gray, whereas a female wold show white tips on the outer rectricies.

Now time to go out and try for an Allen's hummer!

Anna's Hummingbird - Subadult male - Calypte anna

Ducks have been returning to the San Francisco Bay Area for about a month, many of them in the confusing molt between eclipse plumage and the alternate or "bright" plumage of winter and spring. Of course all birds molt, but I don't remember seeing this take place in such vivid detail as on this subadult male Anna's Hummingbird seen this morning along Strawberry Point during a waterbird survey for the Richardson Bay Audubon Center.

These 3 shots were taken in succession. It was amazing to see the array of colors shown by this individual, with a palette that changed with very small changes in his posture. 

Iridescent colors in birds colors produced by the structure of the feather, akin to how colors produced by a thin film of oil on water (interference pattern). Blue colors in birds are also created by feather structure, but by a process that involves the selective scattering of reflected light, based on short wave length.

Those interested in the physical base for these phenomena may want to check these sources:

Why Are Hummingbirds Iridescent? (from Johnsgard book on N.A. Hummingbirds)

The Color of Birds (Stanford)

Structural Color in bird feathers (Wiki, somewhat technical)