This Anna's Hummingbird is apparently a hatch-year male, just growing out his spectacular magenta throat and forehead feathers. The iridescent throat and forehead colors are dependent on the angle of incident light - they can look almost any color from pale green to black! Watch a sitting male in the sun - as it turns its head you will see the colors flash from the "typical" magenta through various other shades. Juveniles, like this hatch-year bird, also do not have the color fully developed.
Anna's are year-round residents at the Gardens, though some apparently still do migrate. Up until the 1970s they were rather rare in winter on the north coast, but from the 80s on they have been quite common (Stanley Harris, "Northwestern California Birds," 2006). We still detect a population drop at this time of year, though, so some are probably still migratory while others have taken up permanent residence. They begin breeding very early and have even been seen collecting nest material in January!
The other common hummingbird at Mendocino Coast Botanical Gardens is the Allen's Hummingbird, easily distinguished by its orange sides and pale chest (it is also noticeably smaller). They begin migrating south in July, and are nearly all gone by mid-September.
It is worth looking closely at hummingbirds in the Gardens, especially during spring or fall migrations, when there is a chance of spotting a Costa's Hummingbird. They are uncommon north of the San Francisco Bay area, but a few have been seen along the coast. Costa's are very similar in appearance to Anna's, and you need a good view of the throat to tell them apart.
Migration season is upon us, and for the next month or so we can hope to find some unusual birds passing through, while the winter residents begin arriving.
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