Ferruginous Hawk

A fairly uncommon Hawk in Sonoma County, usually observed here in the winter months, most often between mid-October and March. Prefers dry, open, grasslands and grassy hillsides. Frequently perches on the ground, unlike most other hawks. Will sometime hunt by sitting next to burrows and waiting for occupants to emerge. Mostly eats small mammals such as ground squirrels, rabbits, and gophers, but also eats snakes, lizards and other reptiles, and even large insects. Tends to hover when hunting. Holds wings in slight dihedral (slight “V”) when soaring. Solitary.

Large (wingspan of about 56 inches, or 1.4m). The largest North American hawk. Blocky head. Broad chest. Generally stocky-looking but with longish, pointed wings, and a broad, fairly long tail (its length a little less than the wing breadth). In a close view of a perched bird, note that the bill is black in all plumages, and the cere (the bump at the base of the bill) and gape are yellow in all plumages. An oft-noted feature of Ferruginous Hawk is the deep gape, which extends as far back as the pupil of the eye.

Ferruginous is a word I remember from reading Moby Dick; the narrator describes a dark interior with paintings on the wall of ferruginous, or rusty brown, tone. The name of this hawk has always seemed less than helpful, though, as we mostly see this and other hawks in flight--and therefore from below--and Ferruginous Hawk is perhaps the palest raptor encountered in Sonoma County when viewed from below, nothing ferruginous about it at all. The color referred to is mostly on the back and on the feathered legs of adult birds. The rusty legs show as a dark “V” on the underside of light-morph adults (juveniles lack this feature).

Identification is complicated by the existence of light and dark morph Ferruginous Hawks, although the light morph is by far the more common (90% of the population, according to Sibley). Light morph birds are reddish to brownish (ferruginous) above and on the legs but pale--nearly white--below. The tail is notably pale as well. the darker feathering on the legs is a distinctive feature, as noted above. The wing linings may be variously spotted. There is usually a dark “comma” on each wing formed by the dark tips of the outermost feathers of the wing linings (see photos). The tips of the primaries are subtly darker and the trailing edge of the adult light morph wing will be slightly darker as well. Despite these features, the plain paleness of the bird is likely to be the overriding impression from an underwing view of an adult light morph Ferruginous Hawk. Seen from above, or turning at a distance, note the light panels in the wings created by pale bases of the primaries. Also note that the base of the tail in light morph birds is noticeably paler than the rest of the tail. Even at great distances, these three pale patches can be easy to see, making a call of Ferruginous Hawk possible. Note, however, that some juvenile Red-Tailed Hawks (Buteo jamaicensis) show a similar pattern. The two should be distinguishable by their very different silhouettes--look for the very short, broad tail of the Red-tailed Hawk and for its much broader wings (photos below).

Juvenile light morph birds are very similar to adults, but will show less spotting on the wing linings and will have pale leg feathering and therefore lack the “V” formed by the dark legs of adult light morph birds. The “commas” may be more apparent in juveniles. Seen from below, the tail usually appears pale, but, with sun streaming through from above, it may have a translucent, rosy-colored look. The bird in the main photo at the top of this page is a fairly typically light morph juvenile.

Dark morph birds are rare. They are all dark, ranging from a dark greyish brown to a dark rusty brown, except for the flight feathers and tail. They are perhaps best identified by silhouette--by general size and shape--when perched. In flight, from below, dark morph Ferruginous Hawks look starkly two-toned with an all-white tail and white flight feathers contrasting strongly with the dark brown head, breast, belly, legs, and wing linings. Because the entire underside of the body and the legs are dark, the “V” formed by the dark leg feathering of light morph adults is not a feature. From above, these birds will show the pale patches at the base of the primaries, as in light morph birds, but the base of the tail will not be pale. As in light morph birds, dark morph adults will show subtly darker primary tips and a subtly darker trailing edge to the wing. Juvenile dark morph birds are similar to dark morph adults.

Selected county sightings: Tolay Lake Regional Park (Feb 9, 2013, Colin Talcroft); Estero Rd. (Feb 1, 2013, Bill Doyle); Hudeman Slough (Jan 31, 2013, Murray Berner); Pepper Rd./Petaluma-Valley Ford Rd. (Dec 8, 2012, Gene Hunn); Adobe Rd./Stage Gulch Rd. (Nov 22, 2012, Gene Hunn); East Railroad Ave. (Oct 28-Nov 6, 2012, Alan Wight); Bodega Farm Pond (Nov 14, 2012, Scott Carey); Carmody Rd. Pond (Nov 11, 2012, Alan Wight); Tolay Lake Regional Park (Nov 11, 2012, Colin Talcroft); Jenner Headlands (Oct. 17, 2012, Kathleen Mugele); Willow Creek Rd. (Oct 16, 2012, Larry Broderick); Stage Gulch Rd. (Sep 19, 2012, Ruth Rudesill); Tolay Lake Regional Park (Mar 3, 2012, Gene Hunn); Skagg’s Island Rd. (Feb 14, 2012, Anthony Cernak)

For current raptor migration information, visit the Golden Gate Raptor Observatory website