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Harris's Hawk

The Harris's Hawk or Harris Hawk, Parabuteo unicinctus, formerly known as the Bay-winged Hawk or Dusky Hawk, is a medium-large bird of prey which breeds from the southwestern USA south to Chile and central Argentina. Birds are frequently reported at large in Western Europe, especially Britain, but it is a popular species in the falconry trade and these records almost certainly all refer to escapes from captivity.

It is the only member of the genus Parabuteo. The name is derived from the Greek para, meaning beside or near, and the Latin buteo, referring to a kind of hawk; uni meaning once; and cinctus meaning girdled, referring to the white band at the base of the tail. John James Audubon gave this bird its English name in honor of his ornithological companion, financial supporter, and friend Edward Harris.

Description

General

Individuals range in length from 46 to 76 cm and generally have a wingspan of 1.1m. In the United States, the average weight for males is about 710g, while the female average is 1020g. This is a sexual dimorphism of about 40%, with the female being larger than the male. They have dark brown plumage with chestnut shoulders, wing linings, and thighs, white on the base a tip of the tail, long, yellow legs and a yellow cere. The vocalizations of the Harris's hawk are very harsh sounds.<

Juvenile

The juveniles are similar to the adults but are more streaked, and when in flight the undersides of the wings are buff-colored with brown streaking.<

Subspecies

There are three subspecies of Harris's Hawks:

P. u. superior: found in Baja California, Arizona, Sonora, and Sinaloa. P. u. superior was believed to have longer tails and wings, and was more blackish in color than P. u. harrisi. However, the sample size of the original study was quite small with only five males and six females. Later research has concluded that there is not as strong a physical difference as was originally assumed. Other ecological differences, such as latitudinal cline were also brought up as arguments against the validity of the subspecies segmentation.
P. u. harrisi: found in Texas, eastern Mexico, and much of Central America.
P. u. unicinctus: found exclusively in South America. It is smaller than the North American subspecies.

Habitat

The bird lives in sparse woodland and semi-desert, as well as marshes (with some trees) in some parts of its range (Howell and Webb 1995), including mangrove swamps, as in parts of its South American range. Harris's Hawks are permanent residents and do not migrate.

Diet

The diet consists of small creatures including birds, lizards, mammals, and large insects. Because it will hunt in groups, the Harris's hawk can also take down larger prey, such as jackrabbits.

Behavior

Nesting and brooding

They nest in small trees, shrubby growth, or cacti. The nests are often compact, made of sticks, plant roots, and stems, and are often lined with leaves, moss, bark and plant roots. They are built mainly by the female. There are usually two to four white to blueish white eggs sometimes with a speckling of pale brown or gray. The nestlings start out light buff, but in five to six days turn a rich brown.

Very often, there will be three hawks attending one nest: two males and one female. Whether or not this is polyandry is debated, as it may be confused with backstanding. The female does most of the incubation. The eggs hatch in 31 to 36 days. The young begin to explore outside the nest at 38 days, and fledge, or start to fly, at 45 to 50 days. The female is sometimes bred two or three times in a year. Young may stay with their parents for up to three years, helping to raise later broods.

Relationship with humans

Hunting

While most raptors are solitary, only coming together for breeding and migration, Harris's Hawks will hunt in cooperative groups of two to six. This is an adaptation to the desert climate in which they live. One hunting technique is when a small group flies ahead, scouts, then the other one flies ahead, and scouts, and this continues until prey is bagged and shared. Another is when all the hawks spread around the prey and one individual flushes it.

The wild Harris's Hawk population is declining due to habitat loss; however, under some circumstances, Harris's Hawks have been known to move into developed areas.

Falconry

These birds have an easy going nature that makes them desirable captive birds. Since about 1980, Harris's Hawks have been increasingly used in falconry and are now the most popular hawks in the West (outside of Asia) for that purpose, as they are the easiest to train and the most affectionate.