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Costa's HummingbirdWhat to look for to tell apart Costa's, Anna's, and Black-chinned Hummingbirds
Contributed by Kenn Kaufman
Published: April 20, 2012  Click to enlarge
Adult males are distinctive if seen well, but females and young birds are plain overall, and they are easily confused with the similar plumages of two other species: Anna’s and Black-chinned.
Shape is a key point for these hummingbirds. Costa’s is a short-tailed bird; when it perches, its wingtips generally extend past the tip of the tail. On Black-chinned and Anna’s, the wingtips usually fall just short of the tail tip. The bill of Costa’s often looks notably thin and is fairly short and slightly curved. The bill of Black-chinned averages longer and often looks heavier and more curved. Anna’s has a fairly short, straight bill, and its relatively large head and thick neck may make the bill seem even shorter.
Size is difficult to judge on a lone bird, but if we study hummers coming to feeders, we can judge comparative sizes. Costa’s averages smaller than its ID contenders, and its short tail adds to that impression. It often has a pot-bellied appearance, especially when hovering.
Female and young Costa’s Hummingbirds typically look drab and pale overall. Their underparts are usually pale gray, almost whitish. Black-chinned Hummingbirds are usually grayer below, and Anna’s tend to be distinctly darker, quite gray on the chest and marked with green along the sides.
Face pattern also holds good clues. Females and young of all three species show a white spot behind the eye. On Costa’s, the spot is usually connected to a vague pale line running behind the dusky ear-coverts. The line is often less obvious on the other two species.
Another detail is the area just above and in front of the eye, or above the eye and the lores. On Costa’s and Anna’s Hummingbirds, a distinct pale line typically separates the eye and lores from the dark forehead. On Black-chinned, the line is usually much less distinct. It’s a subtle difference, but it adds to the overall appearance of the species.
Some of the biggest identification challenges involve recently fledged juveniles. They may be paler or darker than adults, and their bills and tails may not be fully grown, making most of their field marks harder to use. For such birds, we may have to hear diagnostic call notes: a light, thin tic from Costa’s, a harder chip from Anna’s, or a soft, descending tyew from Black-chinned. This point reminds us that bird watching is also a matter of bird listening. |
What to look for
Tail.
Relatively short and (on female and young) rounded at the tip. When perched, the wingtips extend past the tip of the tail.
Bill. Fairly short, thin, very slightly downcurved.
Underparts. Very pale on female and young, almost whitish gray, with very little marking on throat.
Face pattern. Female and young show vague dusky ear patch, ill-defined pale stripe behind eye, narrow pale line above and in front of eye.
Behavior. When hovering, usually flips tail up and down actively.
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Strange migrations
Many birds contradict the simple idea that migration proceeds north in spring and south in fall, and Costa’s Hummingbird tosses out the idea completely. Much of its migration occurs in what we would consider winter and summer, and it may be aligned east and west, not north and south. Furthermore, the migratory patterns of some populations appear to be changing.
The deserts of south-central Arizona make fine habitat for Costa’s, and the species is common there — but for less than half the year. It arrives in numbers in late January and early February and is common through the late winter and most of the spring. Adult males become hard to find after early May, and most of the females and young birds disappear by the middle of June.
Where do the birds go when they leave Arizona? Some may go south into mainland Mexico. However, the late Allan Phillips, who studied Arizona birds for many years, believed that most Costa’s Hummingbirds traveled west and southwest into California and Baja. Evidence for this is still sketchy, but we know from banding returns that the related Anna’s Hummingbird may migrate east and west between southern California and Arizona.
Although the pattern described here still holds for most wild desert areas, increasing numbers of Costa’s now stay year-round in suburban areas of Arizona and California. Apparently, they are lured not only by feeders but by gardens that have blooms at all seasons.
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Kenn Kaufman is the author of the Kaufman Guide to Birds of North
America, Kaufman Field Guide to Advanced Birding, and other books about
birds.
Read more by Kenn Kaufman.
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