| abstract | - The red-tailed hawk (Buteo jamaicensis) is a bird of prey, one of three species colloquially known in the United States as the "chickenhawk," though it rarely preys on standard sized chickens. It breeds throughout most of North America, from western Alaska and northern Canada to as far south as Panama and the West Indies, and is one of the most common buteos in North America. Red-tailed hawks can acclimate to all the biomes within their range. There are fourteen recognized subspecies, which vary in appearance and range. It is one of the largest members of the genus Buteo in North America, typically weighing from 690 to 1,600 g (1.52 to 3.53 lb) and measuring 45–65 cm (18–26 in) in length, with a wingspan from 110–145 cm (43–57 in). The red-tailed hawk displays sexual dimorphism in size, with females averaging about 25% heavier than males. Because they are so common and easily trained as capable hunters, the majority of hawks captured for falconry in the United States are red-tails. Falconers are permitted to take only passage hawks (which have left the nest, are on their own, but are less than a year old) so as to not affect the breeding population. Adults, which may be breeding or rearing chicks, may not be taken for falconry purposes and it is illegal to do so. Passage red-tailed hawks are also preferred by falconers because these younger birds have not yet developed adult behaviors, which would make training substantially more challenging.
- The red-tailed hawk (Buteo jamaicensis) is a bird of prey, one of three species colloquially known in the United States as the "chickenhawk," though it rarely preys on standard sized chickens. It breeds throughout most of North America, from western Alaska and northern Canada to as far south as Panama and the West Indies, and is one of the most common buteos in North America. Red-tailed hawks can acclimate to all the biomes within their range. There are fourteen recognized subspecies, which vary in appearance and range. It is one of the largest members of the genus Buteo in North America, typically weighing from 690 to 1,600 g (1.52 to 3.53 lb) and measuring 45–65 cm (18–26 in) in length, with a wingspan from 110–145 cm (43–57 in). The red-tailed hawk displays sexual dimorphism in size, with females averaging about 25% heavier than males. The bird is sometimes referred to as the red-tail for short, when the meaning is clear in context. The subspecies Harlan's hawk (B. j. harlani) is sometimes considered a separate species (B. harlani). The red-tailed hawk occupies a wide range of habitats and altitudes, including deserts, grasslands, coniferous and deciduous forests, agricultural fields and urban areas. It lives throughout the North American continent, except in areas of unbroken forest or the high arctic. It is legally protected in Canada, Mexico and the United States by the Migratory Bird Treaty Act. Because they are so common and easily trained as capable hunters, the majority of hawks captured for falconry in the United States are red-tails. Falconers are permitted to take only passage hawks (which have left the nest, are on their own, but are less than a year old) so as to not affect the breeding population. Adults, which may be breeding or rearing chicks, may not be taken for falconry purposes and it is illegal to do so. Passage red-tailed hawks are also preferred by falconers because these younger birds have not yet developed the adult behaviors which would make them more difficult to train. As is the case with many raptors, the red-tailed hawk displays sexual dimorphism in size, as females are up to 25% larger than males. As is typical in large raptors, frequently reported mean body mass for Red-tailed Hawks are somewhat higher than expansive research reveals. Part of this weight is highly seasonally variable and due to clinal variation, male red-tailed hawks may weigh from 690 to 1,300 g (1.52 to 2.87 lb) and in females between 900 and 2,000 g (2.0 and 4.4 lb). However, research from nine studies occurring at migration sites in the United States and two breeding studies, one from the smallest race in Puerto Rico, the other from larger races in Wisconsin show that males weigh a mean of 837 g (1.845 lb) and females weigh a mean of 1,040.7 g (2.294 lb), about 15% lighter than prior species-wide published weights. The heaviest surveyed weights came from migrants in Cape May, New Jersey, where females weighed a mean of 1,278 g (2.818 lb), males a mean of 990.8 g (2.184 lb). The lightest were from the breeding population in forest openings of Puerto Rico, where the females and males weighed an average of 1,023 g (2.255 lb) and 795 g (1.753 lb), respectively, also the highest size sexual dimorphism in the species. Size variation in body mass reveals that the red-tailed hawks typically varies only a modest amount, racial variation in average weights of great horned owls show that mean body mass is nearly twice (the heaviest race is about 36% heavier than the lightest known race on average) as variable as that of the hawk (where the heaviest race is only just over 18% heavier on average than the lightest). Males can reportedly measure 45 to 60 cm (18 to 24 in) in total length, females measuring 48 to 65 cm (19 to 26 in) long. The wingspan can range from 105 to 141 cm (41 to 56 in) and, in the standard scientific method of measuring wing size, the wing chord is 325.1–444.5 mm (12.80–17.50 in) long. The tail measures 188 to 258.7 mm (7.40 to 10.19 in) in length. The exposed culmen was reported to range from 21.7 to 30.2 mm (0.85 to 1.19 in) and the tarsus averaged 74.7–95.8 mm (2.94–3.77 in). The middle toe (excluding talon) can range from 38.3 to 53.8 mm (1.51 to 2.12 in), with the hallux-claw (the talon of the rear toe, which has evolved to be the largest in accipitrids) measuring from 24.1 to 33.6 mm (0.95 to 1.32 in) in length. Red-tailed hawk plumage can be variable, depending on the subspecies and the region. These color variations are morphs, and are not related to molting. The western North American population, B. j. calurus, is the most variable subspecies and has three color morphs: light, dark, and intermediate or rufus. The dark and intermediate morphs constitute 10–20% of the population. Though the markings and hue vary across the subspecies, the basic appearance of the red-tailed hawk is consistent. Overall, this species is blocky and broad in shape, often appearing (and being) heavier than other Buteos of similar length. A whitish underbelly with a dark brown band across the belly, formed by horizontal streaks in feather patterning, is present in most color variations. Especially in younger birds, the underside may be otherwise covered with dark brown spotting. The red tail, which gives this species its name, is uniformly brick-red above and light buff-orange below. The bill is short and dark, in the hooked shape characteristic of raptors, and the head can sometimes appear small in size against the thick body frame. They have a relatively short, broad tails and thick, chunky wings. The cere, the legs, and the feet of the red-tailed hawk are all yellow. Immature birds can be readily identified at close range by their yellowish irises. As the bird attains full maturity over the course of 3–4 years, the iris slowly darkens into a reddish-brown hue. In both the light and dark morphs, the tail of the immature red-tailed hawk is patterned with numerous darker bars. The red-tailed hawk is one of the most widely scattered hawks in the Americas. It breeds from central Alaska, the Yukon, and the Northwest Territories east to southern Quebec and the Maritime Provinces of Canada, and south to Florida, the West Indies, and Central America. The winter range stretches from southern Canada south throughout the remainder of the breeding range. Its preferred habitat is mixed forest and field, with high bluffs or trees that may be used as perch sites. It occupies a wide range of habitats and altitudes, including deserts, grasslands, coastal regions, mountains, foothills, coniferous and deciduous woodlands, tropical rainforests, agricultural fields and urban areas. It is second only to the peregrine falcon in the use of diverse habitats in North America. It lives throughout the North American continent, except in areas of unbroken forest or the high Arctic. The red-tailed hawk is widespread in North America, partially due to historic settlement patterns, which have benefited it. The clearing of forests in the Northeast created hunting areas, while the preservation of woodlots left the species with viable nest sites. The increase in trees throughout the Great Plains during the past century due to fire suppression and tree planting facilitated the western range expansion of the red-tailed hawk as well as range expansions of many other species of birds. The construction of highways with utility poles alongside treeless medians provided perfect habitat for perch-hunting. Unlike some other raptors, the red-tailed hawk are seemingly unfazed by considerable human activity and can nest and live in close proximity to large numbers of humans. Thus, the species can also be found in cities, where common prey such as rock pigeons and brown rats may support their populations. One famous urban red-tailed hawk, known as "Pale Male", became the subject of a non-fiction book, Red-Tails in Love: A Wildlife Drama in Central Park, and is the first known red-tail in decades to successfully nest and raise young in the crowded New York City borough of Manhattan. In flight, this hawk soars with wings often in a slight dihedral, flapping as little as possible to conserve energy. Active flight is slow and deliberate, with deep wing beats. In wind, it occasionally hovers on beating wings and remains stationary above the ground. When soaring or flapping its wings, it typically travels from 32 to 64 km/h (40 mph), but when diving may exceed 190 km/h (120 mph). The cry of the red-tailed hawk is a two to three second hoarse, rasping scream, described as kree-eee-ar, that begins at a high pitch and slurs downward. This cry is often described as sounding similar to a steam whistle. The red-tailed hawk frequently vocalizes while hunting or soaring, but vocalizes loudest in annoyance or anger, in response to a predator or a rival hawk's intrusion into its territory. At close range, it makes a croaking "guh-runk". Young hawks may utter a wailing klee-uk food cry when parents leave the nest. The fierce, screaming cry of the red-tailed hawk is frequently used as a generic raptor sound effect in television shows and other media, even if the bird featured is not a red-tailed hawk. The red-tailed hawk is carnivorous, and an opportunistic feeder. Its diet is mainly small mammals, but it also includes birds and reptiles. Prey varies with regional and seasonal availability, but usually centers on rodents, comprising up to 85% of a hawk's diet. Most commonly reported prey types include mice, including both native Peromyscus species and house mice; gophers, voles, chipmunks, ground squirrels and tree squirrels. Additional prey (listed by descending likelihood of predation) include lagomorphs, shrews, bats, pigeons, quail, corvids, waterfowl, other raptors, reptiles, fish, crustaceans, insects and earthworms. Where found in Caribbean islands, red-tailed hawks prey mostly on reptiles such as snakes and lizards, since these are perhaps the most predominant native land animals of that region. Prey specimens can range to as small a size as beetles and worms. However, they can also prey on marmots, white-tailed jackrabbits, or female wild turkey, all of which are at least easily double the weight of most red-tails. Although they prefer to feed on fresh prey they've killed themselves, these hawks are not above occasionally consuming carrion. During winter in captivity, an average red-tail will eat about 135 g (4.8 oz) daily. The red-tailed hawk commonly employs one of two hunting techniques. Often, they scan for prey activity from an elevated perch site, swooping down from the perch to seize the prey. They also watch for prey while flying, either capturing a bird in flight or pursuing prey on the ground until they can pin them down in their talons. Red-tailed hawks, like some other raptors, have been observed to hunt in pairs. This may consist of stalking opposites sides of a tree, in order to surround a tree squirrel and almost inevitably drive the rodent to be captured by one after being flushed by the other hawk. They are opportunistically attracted to conspicuous meals, such as displaying male red-winged blackbirds. The great horned owl occupies a similar ecological niche nocturnally to the red-tail, taking similar prey. Competition may occur between the hawk and owl species during twilight, although the differing nesting season and activity times usually results in a lack of direct competition. Although the red-tail's prey is on average larger (due in part to the scarcity of diurnal squirrels in the owl's diet), the owl is an occasional predator of red-tailed hawks themselves, of any age, while the hawks are not known to predate adult great horned owls. Other competitors include other large Buteo species such as Swainson's hawks and rough-legged hawks, as well as the northern goshawk, since prey and foraging methods of these species occasionally overlap. Hawks have been observed following American badgers to capture prey they flush and the two are considered potential competitors. Competition over carcasses may occur with American crows, and several crows working together can displace a hawk. Larger raptors, such as eagles and ferruginous hawks, may steal hawk kills. The red-tailed hawk reaches sexual maturity at two years of age. It is monogamous, mating with the same individual for many years. In general, the red-tailed hawk will only take a new mate when its original mate dies. The same nesting territory may be defended by the pair for years. During courtship, the male and female fly in wide circles while uttering shrill cries. The male performs aerial displays, diving steeply, and then climbing again. After repeating this display several times, he sometimes grasps her talons briefly with his own. Courtship flights can last 10 minutes or more. Copulation often follows courtship flight sequences, although copulation frequently occurs in the absence of courtship flights. In copulation, the female, when perched, tilts forward, allowing the male to land with his feet lodged on her horizontal back. The female twists and moves her tail feathers to one side, while the mounted male twists his cloacal opening around the female's cloaca. Copulation lasts 5 to 10 seconds and during pre-nesting courtship in late winter or early spring can occur numerous times each day. In the same period, the pair constructs a stick nest in a large tree 4 to 21 m (13 to 69 ft) off the ground or on a cliff ledge 35 m (115 ft) or higher above the ground, or may nest on man-made structures. The nest is generally 71 to 97 cm (28 to 38 in) in diameter and can be up to 90 cm (3.0 ft) tall. The nest is constructed of twigs, and lined with bark, pine needles, corn cobs, husks, stalks, aspen catkins, or other plant lining matter.Great horned owls compete with the red-tailed hawk for nest sites. Each species has been known to kill the young and destroy the eggs of the other, but in general, both species nest in adjacent or confluent territories without conflict. Great horned owls are incapable of constructing nests and typically expropriate existing red-tail nests. Great horned owls begin nesting behaviors much earlier than red-tails, often as early as December. Red-tails are therefore adapted to constructing new nests when a previous year's nest has been overtaken by owls or otherwise lost. New nests are typically within a kilometer or less of the previous nest. Often, a new nest is only a few hundred meters or less from a previous one. Being a large predator, most predation of these hawks occurs with eggs and nestlings, which are taken by owls, corvids and raccoons. A clutch of 1 to 3 eggs is laid in March or April, depending upon latitude. Clutch size depends almost exclusively on the availability of prey for the adults. Eggs are laid approximately every other day. The eggs are usually about 60 mm × 47 mm (2.4 in × 1.9 in). They are incubated primarily by female, with the male substituting when the female leaves to hunt or merely stretch her wings. The male brings most food to the female while she incubates. After 28 to 35 days, the eggs hatch over 2 to 4 days; the nestlings are altricial at hatching. The female broods them while the male provides most of the food to the female and the young, which are known as eyasses (pronounced "EYE-ess-ez"). The female feeds the eyasses after tearing the food into small pieces. After 42 to 46 days, the eyasses begin to leave the nest. The fledging period follows, with short flights engaged in, after another 3 weeks. About 6 to 7 weeks after fledging, the young begin to capture their own prey. Shortly thereafter, when the young are around 4 months of age, they become independent of their parents. However, the hawks do not generally reach breeding maturity until they are around 3 years of age. In the wild, red-tailed hawks have lived for at least 25 years, for example, Pale Male was born in 1990, and in Spring 2014 is still raising eyasses. The oldest captive hawk of this species was at least 29 and a half years of age.
|
