Harris's Hawk

Parabuteo unicinctus

Taxonomy:
Class: Aves
Order: Falconiformes
Family: Accipitridae
Subfamily: Buteoninae
Genus: Parabuteo

Length: 18-24 in.
Weight: 1-2 lbs. (male); 1.75-3.5 lbs. (female)
Wingspan: 40-47 in.

Common Names: bay-winged hawk, dusky hawk

Etymology: para (Greek) - "beside or near"; uni (Latin) - "once"; cinctus (Latin) - "girdled," a reference to white band at base of tail

Description: The Harris's hawk is a boldly marked, tricolored, medium-large buteo with long legs and naked lores. Bill large, light blue with a black tip. Plumage coloration bold - dark brown to sooty black. Upper wing-coverts, wing lining, and flanks rusty to chestnut red. Tail dark brown to almost black with white base and terminal band. Iris dark brown. Tarsi, toes, cere, and orbit bright yellow. Harris's hawk juveniles are similar to adults, except underparts streaked with cream or buffy coloration. Eye color changes from dark brown to light brown in second year.

Flight: Normal flight is flap-flap-glide, flap-flap-glide (accipiter-like). Wing beats are fewer and slower than accipiters and glides are longer. When not hunting, flight may appear sluggish, but they are known for rapid acceleration, agility, and ability to "hug" landscape and maneuver around obstacles. Also, soars at high altitudes and displays dramatic dives. Males are especially agile; under the right conditions, they may fly backward and hover briefly; females are more directional in flight and give impression of speed and power.

Voice: Poorly studied. Alarm Call - angry sounding, prolonged, harsh note that loses intensity, irr or uierr.

Habitat: Semi-open desert scrub, savanna, grassland, and wetland habitats. Scattered larger trees or other features apparently provide important perches and nest support.

Distribution: Range in United States currently restricted to isolated populations in Arizona, New Mexico and Texas.

Nesting: This species nests in social units that vary from an adult pair to as many as seven individuals, both adults and immatures. Groups exhibit monogamy and polyandry, and sometimes polygamy. They are able to breed year-round in temperate climate desert habitats in North America. Although most Harris's hawks nest in spring, some females will lay second and third clutches. Nests are located in almost any tall, sturdy structure. Both breeding members build nest and may have as many as four nests. Lay 1-5 eggs (usually 3-4) that are pale bluish (rapidly fades to white), plain or with spots of pale brownish or lavender. Incubation period is 31-36 days. Female does incubation, male supplies female with food, helps with incubation, and chases predators. Auxiliary birds participate in hunts and harassment of predators. Groups with helpers rear slightly larger nestlings and initiate second nests more frequently than pairs. Unrelated helpers may occasionally sire offspring and may inherit breeding territories upon the death of breeding hawk of the same sex. Harris's hawks branch at about 40 days of age; males fledge significantly earlier than females. Fledglings remain in the nesting territory for at least 2-3 months.

Food: Harris's hawks employ one of the most sophisticated cooperative hunting strategies in birds. Hunts medium-sized to relatively large mammals (hares and rabbits), birds, and lizards. Two methods of hunting: 1) sit and wait (often employed by lone hawks); 2) short-flight-perch hunting. Cooperative tactics include (1) surprise pounce - several hawks coming from different directions; (2) flush and ambush - 1 or more hawks penetrate the cover while others watch from nearby perches and attack when prey is flushed; (3) relay attack - long chase of hares while the lead "chase" position is alternated among hunting birds. Energetic analysis shows the maximum food availability per individual is obtained by groups of 5 hawks, the most common size. They feed in order of dominance; alpha breeding female (most dominant), alpha breeding male, beta male, and 0-4 birds. During nonbreeding season, a group of hawks will guard/feed on a large carcass for more than 36 hours, and cache carcasses.