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Status: Population size: 390,000

Harris's Hawk
(Parabuteo unicinctus)

The Harris's Hawk was on the 2002 WatchList, but is not on the 2007 WatchList. Please refer to http://web1.audubon.org/science/species/watchlist/techReport.php for information on the 2007 WatchList.

Unique among raptors for its cooperative hunting, Harris's Hawk displays one of the most advanced group hunting tactics among birds. A resident species whose range barely extends into the southern US, it is threatened by habitat loss and degradation.

Identification
Harris's is a dark brown hawk with white tail-coverts and white at the base of the tail. The upper wing-coverts, wing lining, and flanks are rusty or chestnut colored. Its bill is light blue with a black tip. As with other raptors, females are larger than males. Juveniles are similar to adults but have a less rufous coloring, buffy spots on the belly, white under the wing, and lots of dusky barring on the tail.

Distribution and Population Trends
The range of Harris's Hawks only extends into southern US in Texas, Arizona, and New Mexico. The remainder of its range is restricted to desert habitats throughout Mexico and Central America. It is a resident of several Mexican Important Bird Areas, including the Sierra de San Carlos and Monte Escobedo IBAs. It can also be found in savannas and semi-open areas throughout South America to southern Chile. Its range in the US has been reduced because of urbanization of river valleys and deserts. Christmas Bird Count data in Texas collected from 1957-1984 indicated a 68% decline of Harris's Hawks. Similar data is not available for Arizona or New Mexico, but loss of habitat and prey base have probably had negative impacts on their populations in those states as well.

Ecology
Mostly a nonmigratory species, but there may be some north-south movement in some South American populations. Breeding occurs in desert scrub, savanna, grassland, and wetland habitats. Saguaro cacti and scattered trees provide perches and nesting places. Areas inhabited by Harris's tend to have higher densities of trees than surrounding habitat, and they may prefer areas near open water, especially in hot climates. Harris's will attempt to breed two, sometimes three, times each year, so it's not surprising that they have been known to breed every month of the year. Nests are constructed in tall structures, usually saguaro cacti, paloverde and mesquite trees, and live oak, but have nested on a transmission tower, cliffs, and artificial platforms. The height of hatching season is April-May. Harris's lays 3-4 eggs that are incubated for 31-36 days with hatching spread over 2-4 days (asynchronous). Coyotes and Common Ravens prey upon young hawks. Great Horned Owls prey upon both young and adults.

Harris's Hawks prey upon birds, lizards, and mammals such as hares and rabbits. This is the only North American raptor known to hunt in groups, and it is the most advanced form of cooperative hunting known among birds. Groups consist of two to seven individuals, usually a pair and their offspring. Harris's use three methods to cooperatively hunt. One method involves several hawks pouncing on a prey item where there is no cover. In a second method, one hawk will flush prey from cover while other hawks capture the flushed prey. Lastly, hawks will take turns in the lead position of long prey chases. If a hawk misses the prey, a second is prepared to try soon after. Alternatively, a second hawk will come from the opposite direction to intercept the prey. Captured prey can be guarded for more than a day and a half from other predators, a form of storing food. Lone Harris's Hawks hunt by searching for prey from a perch and by taking frequent short flights between perches, but group hunting is more successful. Helpers also contribute to the success of the breeding pair by providing food and deterring predators throughout the breeding season.

Threats
The largest threat to this species is habitat degradation and loss. Mesquite and brush control practices, and loss of habitat to urban and oil and gas development degrade and/or destroy habitat. Hunting and off-road vehicles near nesting habitats cause parents to abandon their nest, resulting in loss of eggs and young. Harris's are electrocuted in areas with a high density of electrical wires. Drowning, illegal trapping, and shooting are additional modes of death.

Conservation
A reintroduction program took place from 1979-1989 in the lower Colorado River valley. Almost 200 Harris's were released to the area. There was initial success with 5 pairs actually yielding offspring. However, the restoration effort did not coincide with habitat restoration and long-term survival of the population is unlikely.

Management recommendations have been made, but not carried out. The species would probably benefit from being federally listed, even if just as a species of Special Concern. Human disturbance near nesting areas should be limited, perhaps to the extent of creating areas where no human disturbance is allowed (a raptor management area). A monitoring program should be instituted to help better understand the causes for this species decline and how to increase populations in the US. Habitat restoration and education programs should also be established.

What Can You Do?
Volunteers are crucial to the success of programs that monitor the long-term status of wintering populations of Harris's Hawk and other bird species. Audubon's Christmas Bird Count (CBC) is one of the longest-running citizen-science monitoring programs in the world and has helped to follow changes in the numbers and distribution of Harris's Hawk. To learn more about the CBC and how you can participate, visit: http://www.audubon.org/bird/cbc

Audubon's Important Bird Areas program is a vital tool for the conservation of Harris's Hawks as well as other species. To learn more about the Important Bird Areas program, and how you can help, visit: http://www.audubon.org/bird/iba/.

Information on where Harris's Hawks occur and in what numbers is vital to conserving the species. Help in monitoring this and other species by reporting your sightings to eBird. A project of Audubon and the Cornell Lab or Ornithology, eBird is the world's first comprehensive online bird monitoring program: http://www.audubon.org/bird/ebird/index.html

References
Bednarz, J. C. 1995. Harris's Hawk (Parabuteo unicinctus). In The Birds of North America, No. 146 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.