Like all hawks, Harris' hawks have keen vision and hearing. They are known to make hissing noises, give alarm calls, and probably communicate visually as well.
Communication Channels: visual ; acoustic
Perception Channels: visual ; tactile ; acoustic ; chemical
Harris's Hawks are not listed as threatened or endangered. They are included in CITES appendix II and they are protected from harassment and illegal shooting by the Migratory Bird Treaty Act. A population on the Colorado River is thought to have been extirpated due to their dependence on a riparian community which was altered by dam construction and disturbance from dredging as well as nest destruction. Real estate and agriculture threaten the species in Arizona. Recent declines in Texas populations resulted from the clearing of mesquite for agriculture and livestock grazing. Habitat loss is the major cause of decline of this species as well as excessive human disturbance. Shooting can result in nest failure, abandonment and mortality. Electrocution is responsible for the loss of half of the population of breeding hawks. It is possible in areas such as Arizona for birds to live in cities where the native vegetation is protected, houses are spread apart and there is not an overabundant amount of asphalt and concrete.
US Migratory Bird Act: protected
US Federal List: no special status
CITES: appendix ii
IUCN Red List of Threatened Species: least concern
The only negative impact of these hawks is their habit of congregating on electrical transformers, where they are often electrocuted. This has become a great cost to electric companies who are being forced to reinsulate and, in some cases, build arms for perching to reduce the mortality rates of hawks.
Harris' hawks are of great benefit to farmers whose crops are destroyed by rodents. These hawks feed primarily on small rodents such as mice and rats and therefore alleviate a lot of destruction to crops.
Positive Impacts: controls pest population
Harris' hawks are important predators in their ecosystem, controlling populations of many small mammal species.
The diet of Harris' hawks is versatile and varies with prey availability. These hawks feed mostly on small mammals such as rats and mice, but also take birds and lizards. They commonly hunt in groups of about five hawks, increasing their success rate and enabling them to take larger prey such as cottontails and jack rabbits. These hunting groups consist of a breeding pair and other helpers, with the female dominating. They are fast flyers and once they have spotted their prey, they land and take turns trying to scare and actually flush the prey animal until it darts from beneath its hiding place. Another member of the hunting group captures the animal and assumes a posture known as mantling, in which the hawk shields the prey with its wings to hide it from other birds. It has been suggested that group hunting is encouraged by the dense brush and thorny nature of their habitat. There is some evidence that these hawks may feed on carrion if food availability is low.
Animal Foods: birds; mammals; reptiles
Primary Diet: carnivore (Eats terrestrial vertebrates)
Harris' hawks can be found in semi-open habitats in the southwestern United States and northwestern Mexico, from Baja California to southern Arizona, New Mexico and Texas, extending south through Central and South America to Chile and just into Patagonia.
Biogeographic Regions: nearctic (Native ); neotropical (Native )
Harris' hawks are found in various habitats, from upland desert dominated by saguaros to mesquite, palo verde, and ironwood woodlands in the Colorado River valley. There is a population of hawks being reintroduced to the Colorado River that prefer to nest near water in mequite, willows and cottonwoods. In urban areas, they are seen utilizing washes, open lots, and open desert. These hawks may be found at elevations of 400 to 1,000 meters.
Range elevation: 400 to 1,000 m.
Habitat Regions: temperate ; tropical
Terrestrial Biomes: desert or dune ; savanna or grassland ; scrub forest
Other Habitat Features: urban ; suburban ; riparian
Records on longevity are collected from the Bird Banding Laboratory (BBL) in Laurel, Maryland. The maximum longevity record for Harris' hawks is 14 years, 11 months.
Range lifespan
Status: wild: 14.9 (high) years.
Average lifespan
Status: wild: 179 months.
These are large hawks with long tails and broad wings. Harris's hawks range in length from 18 to 23 inches (46 to 76 cm) and have wingspans of 40 to 47 inches (100 to 120 cm). Adult plumage is uniformly chocolate brown with distinct reddish shoulders, upper and underwing coverts, and leg feathers. The tail is dark with white upper and undertail coverts and a white base and terminal band. Juveniles are similar to adults but are less distinctly colored and have a white belly with chocolate brown streaking. The tarsal feathers are pale with reddish barring and there is barring on the tail and wings. Females weigh an average of 1,047 grams, and males are smaller, weighing an average of 735 grams.
Range mass: 735 to 1047 g.
Range length: 46 to 76 cm.
Range wingspan: 100 to 120 cm.
Sexual Dimorphism: female larger
Other Physical Features: endothermic ; bilateral symmetry
Great horned owls (Bubo virginianus) pose the greatest predation threat to this species, but coyotes (Canis latrans) and common ravens (Corvus corax) also threaten young hawks. Female Harris' hawks utilize helpers to protect their nests. The helpers perch in saguaros and scan the surroundings for predators. They tend to become excited and will use an alarm call when predators come within their nesting area. Groups consisting of 2 to 5 hawks will attack and harass any predator threatening the nest. The alpha male is most likely to strike the predator as the female stays behind to protect the nest. This establishment of helpers greatly increases the detection of predators and nest success.
Known Predators:
Most often, social groups of Harris' hawks contain a single monogamous breeding pair. However, these hawks are known to practice simultaneous polyandry, where more than one male mates with one female and shares in the responsibilities of raising offspring. Polyandry is commonly found in areas where the habitat quality is rich as opposed to arid habitats where the chances of reproductive success are less, even when there are three adults hunting. It is also found to be common in Arizona where the sex ratio is significantly skewed towards males, in comparison with areas such as Texas, where the sex ratio is not as skewed.
Mating System: monogamous ; polyandrous ; cooperative breeder
Harris' hawks build their nests in saguaros, palo verdes and mesquite trees at an average height of 5 meters. In urban areas, nests can be found on cottonwoods, ironwoods, palm trees and electrical towers. Nests are platforms made of sticks, weeds, twigs, and are usually lined with soft mosses, grasses and roots. Between two and four eggs are laid at a time. Females have the ability to breed all year long and can lay two to three clutches within a year. The incubation period lasts about 35 days and the males often share duties with the female during this period. Fledging occurs after another 40 days. The young birds tend to stay around the nest area for two to three months longer.
Breeding interval: Harris' hawks breed two to three times per year.
Breeding season: Harris' hawks breed year round.
Range eggs per season: 3 to 15.
Average eggs per season: 6.
Range time to hatching: 33 to 37 days.
Range fledging age: 35 to 45 days.
Average time to independence: 2-3 months.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; oviparous
Average eggs per season: 3.
Both the female and the male contribute to parental care. Harris' hawks practice cooperative breeding, with several birds helping with building nests, incubation, feeding, and defense. This assistance increases nest success. There is often a trio consisting of two males and a female which aid in the nest cycle.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)
The Harris's hawk (Parabuteo unicinctus), formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south to Chile, central Argentina, and Brazil. This bird is sometimes reported to be at large in Western Europe, especially Britain, but it is a popular species in falconry and these records almost invariably 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.[2] John James Audubon gave this bird its English name in honor of his ornithological companion, financial supporter, and friend Edward Harris.[3]
The Harris's hawk is notable for its behavior of hunting cooperatively in packs consisting of tolerant groups, while other raptors often hunt alone. Harris hawks' social nature has been attributed to their intelligence, which makes them easy to train and have made them a popular bird for use in falconry.[4]
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).[5][6] These hawks have a brownish plumage, reddish shoulders and tail feathers with a white base and white tip.[7]
They exhibit sexual dimorphism with the females being larger by about 35%. 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).[8][9] They have dark brown plumage with chestnut shoulders, wing linings, and thighs,[10] white on the base and tip of the tail,[11] long, yellow legs and a yellow cere.[12] The vocalizations of the Harris's hawk are very harsh sounds.[5]
The lifespan of the Harris's Hawk is 10-–12 years in the wild, 20–25 years in captivity.[13]
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-colored with brown streaking. They can look unlike adults at first glance, but the identical chestnut plumage is an aid for identification.[12]
There are three subspecies of the Harris's hawk:
Harris's hawks live in sparse woodland and semi-desert, as well as marshes (with some trees) in some parts of their range (Howell and Webb 1995), including mangrove swamps, as in parts of their South American range.[16] Harris's hawks are permanent residents and do not migrate.[15] Important perches and nest supports are provided by scattered larger trees or other features (e.g., power poles, woodland edges, standing dead trees, live trees, and boulders, and saguaros).[17]
The wild Harris's hawk population is declining due to habitat loss; however, under some circumstances, they have been known to move into developed areas.[18]
This species occurs in relatively stable groups. A dominance hierarchy occurs in Harris's hawks, wherein the mature female is 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.[19] No other bird of prey is known to hunt in groups as routinely as this species.[20]
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.[21]
Very often, there will be three hawks attending one nest: two males and one female.[22] Whether or not this is polyandry is debated, as it may be confused with backstanding (one bird standing on another's back).[23] 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.[21] 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. No accounts show predation on adults in the United States and the Harris's hawk may be considered an apex predator, although presumably predators like eagles and great horned owls would be capable of killing them.[24] In Chile, black-chested buzzard-eagles (Geranoaetus melanoleucus) are likely predators.[25]
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.[22] 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).[26][27][28] The desert cottontail (Syvilagus auduboni), the leading prey species in the north of the Harris's hawk's range, usually weighs 800 g (1.8 lb) or less.[29] 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.[9] 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.[30][31][32][33][34]
In the Southwestern United States, the most common prey species (in descending order of prevalence) are desert cottontail (Syvilagus auduboni), eastern cottontail (Syvilagus floridanus), black-tailed jackrabbit (Lepus californicus), ground squirrels (Ammopsermophilus spp. and Spermophilus spp.), woodrats (Neotoma spp.), kangaroo rats (Dipodomys spp.), pocket gophers (Geomys and Thomomys spp.), Gambel's quail (Callipepla gambelii), scaled quail (C. squamata), northern bobwhite (Colinus virginianus), cactus wren (Campylorhynchus brunneicapillus), northern mockingbird (Mimus polyglottos), desert spiny lizards (Sceloporus magister), and skinks (Eumeces spp.)[35][36] In the tropics, Harris's hawks have adapted to taking prey of several varieties, including those like chickens and European rabbits introduced by man.[37][38] In Chile, the common degu (Octodon degus) makes up 67.5% of the prey.[39]
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 believed to be an adaptation to the lack of prey in 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 bird flushes it out.[40] Harris's hawks will often chase prey on foot, and are quite fast on the ground and their long, yellow legs are adapted for this, as most hawks don't spend as much time on the ground. Groups of Harris's hawks tend to be more successful at capturing prey than lone hawks, with groups of two to four individuals having ~10% higher success rates per extra individual.[41]
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 one of the easiest to train and the most social.[42]
Trained Harris's hawks have been used to remove an unwanted pigeon population from London's Trafalgar Square, and from the tennis courts at Wimbledon.[43]
Trained Harris's hawks have been used for bird abatement by falconry experts in Canada and the United States at various locations including airports, resorts, landfill sites, and industrial sites.[44]
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Harris's hawk in flight at a falconry centre
Harris's hawk at a licensed falconry centre, Ontario, Canada
John James Audubon illustrated the Harris's hawk in The Birds of America (published in 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).[45]
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{{cite journal}}: Cite journal requires |journal= (help) The Harris's hawk (Parabuteo unicinctus), formerly known as the bay-winged hawk, dusky hawk, and sometimes a wolf hawk, and known in Latin America as peuco, is a medium-large bird of prey that breeds from the southwestern United States south to Chile, central Argentina, and Brazil. This bird is sometimes reported to be at large in Western Europe, especially Britain, but it is a popular species in falconry and these records almost invariably 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 honor of his ornithological companion, financial supporter, and friend Edward Harris.
The Harris's hawk is notable for its behavior of hunting cooperatively in packs consisting of tolerant groups, while other raptors often hunt alone. Harris hawks' social nature has been attributed to their intelligence, which makes them easy to train and have made them a popular bird for use in falconry.
