Hawks Are Difficult

I often find hawks difficult to identify. Color morphs, sex differences and age variations can confuse me, particularly when a hawk will not cooperate by remaining stationary. Usually when I see an interesting hawk I begin to snap photographs and later try to identify the species.

This spring a pair of Swainson’s hawks (Buteo swainsoni) are spending time in an abandoned apple orchard on the Ash Creek Wildlife Refuge (Modoc County CA). These two hawks are rather tame and allow me the opportunity to study them. I cannot find a nest nearby, the hawks appear to simply like the perch these trees provide.

A long-distant migrant, Swainson’s hawks breed in western North America and winter primarily in Argentina. Each spring Leonard and I look forward to their return to the open grasslands and agricultural areas where they hunt the small mammals and insects (primarily grasshoppers and caterpillars) which comprise the majority of their diet. Small birds and snakes are also taken.

The plumage of Swainson’s hawks is quite variable. There are light, intermediate and dark morphs graded evenly across the spectrum. The sexes are generally similar with  females being larger. Swainson’s hawks have a light belly, rufous chest and are grey or brown on the upper side – males usually grey headed and females more often with brownish heads. Tails are grey with a dark subterminal band and many thinner dark bands. The underwings have white wing linings and black flight feathers. Except for the dark morphs, most adult Swainson’s hawks have a pale throat and whitish forehead. This white coloration is useful in identifying a Swainson’s hawk. Another distinguishing feature is that the gape does not reach the leading edge of the eye.

Interestingly, this hawk was first illustrated by William Swainson in Canada in 1827. However, Swainson misidentified the hawk and apparently confused it with a vulture. Eventually, when the Swainson’s hawk was determined to be a new species it was still named after its first illustrator.

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