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 United States south to Chile and central Argentina. Birds are sometimes reported at large in Western Europe, especially Britain, but it is a popular species in falconry 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, near or like, and the Latin buteo, referring to a kind of buzzard; 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.
The Harris Hawk is famous for its remarkable behavior of hunting cooperatively in “packs”, consisting of family groups. (Most raptors are solitary hunters.)
Individuals range in length from 46 to 76 cm (18 to 30 in) and generally have a wingspan of 1.1 m (3.6 ft) They exhibit sexual dimorphism with the females being larger by about 40%. In the United States, the average weight for males is about 710 g (25 oz), while the female average is 1,020 g (36 oz)..
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.
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.
There are three subspecies of Harris’s Hawk:
- P. u. superior: found in Baja California, Arizona, Sonora, and Sinaloa. P. u. superior was believed to have longer tails and wings and to be more blackish 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.
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.
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.
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 (one bird standing on another’s back). 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 sometimes breeds two or three times in a year. Young may stay with their parents for up to three years, helping to raise later broods.
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.
In one hunting technique, a small group flies ahead and scouts, then another group member flies ahead and scouts, and this continues until prey is bagged and shared. In another, 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.
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 social.
John James Audubon illustrates the Harris’s Hawk in Birds of America (published, London 1827-38) as Plate 392 with the title “Louisiana Hawk –Buteo harrisi“. The image was engraved and colored by the Robert Havell, London workshops in 1837. The original watercolor by Audubon was purchased by the New York History Society where it remains to this day (January 2009).
- BirdLife International (2004). Parabuteo unicinctus. 2006. IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 10 May 2006. Database entry includes justification for why this species is of least concern
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