Harris’s hawk (Parabuteo unicinctus)

Oct 01, 2017 Features / Columnists, Interesting Creatures in Guyana

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The Harris’s hawk (Parabuteo unicinctus) formerly known as the bay-winged hawk or dusky hawk, is a medium-large bird of prey that breeds from the south-western United States south to Chile, central Argentina, and Brazil. 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.
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 tip of the tail. John James Audubon gave this bird its English name in honour of his ornithological companion, financial supporter, and friend Edward Harris.
The Harris’s hawk is notable for its behaviour of hunting cooperatively in packs consisting of tolerant groups, while other raptors often hunt alone. It is the Harris’s hawk’s intelligence that leads to its social nature, which results in easier training and has meant that Harris’s hawks have become a popular bird for use in falconry.
This medium-large hawk is roughly intermediate in size between a peregrine falcon (Falco peregrinus) and a red-tailed hawk (Buteo jamaicensis). Harris’s hawks range in length from 46 to 59 cm (18 to 23 in) and generally have a wingspan of about 103 to 120 cm (41 to 47 in).
They exhibit sexual dimorphism with the females being larger by about 35 percent. In the United States, the average weight for adult males is about 701 g (1.545 lb), with a range of 546 to 850 g (1.204 to 1.874 lb), while the adult female average is 1,029 g (2.269 lb), with a range of 766 to 1,633 g (1.689 to 3.600 lb).
They have dark brown plumage with chestnut shoulders, wing linings, and thighs, white on the base and tip of the tail, long, yellow legs and a yellow cere. The vocalizations of the Harris’s hawk are very harsh sounds.
The juvenile Harris’s hawk is mostly streaked with buff, and appears much lighter than the dark adults. When in flight, the undersides of the juveniles’ wings are buff-coloured with brown streaking. They can look unlike adults at first glance, but the identical chestnut plumage is an aid for identification.
The population is declining due to habitat loss; however, under some circumstances, they have been known to move into developed areas.
This species occurs in relatively stable groups. A dominance hierarchy occurs in Harris’s hawks, wherein the mature female is at the dominant bird, followed by the adult male and then the young of previous years. Groups typically include from two to seven birds. Not only do birds cooperate in hunting, they also assist in the nesting process. No other bird of prey is known to hunt in groups as routinely as this species.
The diet of the Harris’s hawk consists of small creatures including birds, lizards, mammals, and large insects. Because it often hunts in groups, the Harris’s hawk can also take down larger prey.
Although not particularly common, the Harris’s hawk may take prey weighing over 2 kg (4.4 lb), such as adult jackrabbits, great blue heron (Ardea herodias) and half-grown wild turkeys (Meleagris gallapavo).The desert cottontail (Syvilagus auduboni), the leading prey species in the north of the Harris’s hawk range, usually weighs 800 g (1.8 lb) or less. Undoubtedly because it pursues large prey often, this hawk has larger and stronger feet, with long talons, and a larger, more prominent hooked beak than most other raptors around its size. Locally, other buteonine hawks, including the ferruginous hawk, the red-tailed hawk and the white-tailed hawk also hunt primarily cottontails and jackrabbits, but each are bigger, weighing about 500 g (18 oz), 300 g (11 oz) and 200 g (7.1 oz), respectively, more on average than a Harris’s hawk.
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 bluish white eggs sometimes with a speckling of pale brown or grey. 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. The young may stay with their parents for up to three years, helping to raise later broods.
Nests are known to be predated by coyotes (Canis latrans), golden eagles (Aquila chrysaetos), red-tailed hawks (Buteo jamaicensis), great horned owls (Bubo virginianus) and flocks of common ravens (Corvus corax), predators possibly too formidable to be fully displaced by the Harris’s hawk’s cooperative nest defenses. In Chile, black-chested buzzard-eagles (Geranoaetus melanoleucus) are likely predators. [Source: Wikipedia]

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