Cooper's Hawk, Accipiter cooperii

Cooper's Hawk
Cooper's Hawks are year-round residents of the Bay Area. They are accipiters, with long tails and short rounded wings, adapted to pursue their favorite prey, smaller birds, through wooded areas. They are quite a bit more common here than the similar but smaller Sharp-shinned Hawk. Sharpies winter here but mostly depart to breed elsewhere; I have few pictures of them, many of Coops.

The two species present a well-known identification challenge, but there are a number of good distinguishing features. Coops' legs are thicker, roughly pencil-thick vs. toothpick-thin in Sharpies. The head is proportionately larger and blocky-shaped on the Coop, with the eye looking smaller and more forward. The difference in head size is especially noticeable in flight, with the Coop's head projecting well forward from the bend in the wing. Another flight difference is the slower flap speed of the larger Coops. Coops' outermost tail feathers
are shorter than the rest, often producing a rounded look to the tail tip, compared to Sharpies' typically square tip.

Adult female above; year-old male, closely resembling an adult, below. The upperparts of females are brownish-gray, those of males bluish-gray. The rufous barring on the underparts of males tends brighter and more red, on females duller and more brown. Females are notably larger, but size can be difficult to estimate unless both sexes are seen together.

Cooper's Hawk

Cooper's Hawk, 3/5/05, Arastradero Preserve
A good view of the Coop's curved tail-tip; the outermost tail feather is shorter
than the inner ones.

Cooper's Hawk
The image above is a digiscope, one of the earliest of my pictures posted on this site.

Cooper's Hawk
This is the same bird that is shown about a month later in nearly complete adult plumage
in the second image down from the top of this page. Here the bird is shown in mid-molt,
the head still with the the juvenal brown-gray striping, the eye an orange hue midway
between the pale yellow of the juvenile and adult red, the back and wing feathers mostly
adult gray but still with a number in juvenal brown. For full juvenal plumage, see the
birds pictured below.

Cooper's Hawk, juvenile, 11/23/06, Stevens Creek north of 101
As with most species, I have proportionally more pictures of juvenile
than of adult Cooper's; birds learn to be more cautious as they get older.  
In common with other raptors, Cooper's Hawks hold their juvenal plumage
through their entire first year.

Cooper's Hawk, juvenile, 9/20/10, Arastradero Preserve

Cooper's Hawk, juvenile, 8/3/10, Arastradero Preserve

Cooper's Hawk
Above and below, a juvenile, having just captured a vole and carrying it in a clump of grass, and standing in the grass.

Cooper's Hawk

Cooper's Hawk, juvenile, with American Crow, 11/29/10, Shoreline Park, Mountain View
This juvenile Cooper's Hawk was being harassed by several American Crows, including the one shown out-of-focus here, and shortly after I took this photo, the hawk left this perch.

Cooper's Hawk, nestling, 6/21/07, Arastradero Preserve
Above, a Cooper's nestling, nearly fledged but still with some tufts of down, at Arastradero Preserve in June 2007; below, another at virtually the same stage of development but standing out on a branch near the nest, in a residential yard in Cupertino, June 2009.

Cooper's Hawk, nestling, 6/18/09, Cupertino