Busardo Colirrojo

Identificación

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 main color morphs: light, dark, and intermediate or rufous. The dark and intermediate morphs constitute 10–20% of the population in the Western United States, but seem to constitute only 1–2% of B. j. calurus in western Canada. A whitish underbelly with a dark brown band across the belly, formed by horizontal streaks in feather patterning, is present in most color variations. This feature is variable in eastern hawks and generally absent in some light subspecies (i.e. B. j. fuertesi). Most adult red-tails have a dark-brown nape and upper head, which gives them a somewhat hooded appearance, while the throat can variably present a lighter brown "necklace". Especially in younger birds, the underside may be otherwise covered with dark-brown spotting, and some adults may too manifest this stippling. The back is usually a slightly darker brown than elsewhere with paler scapular feathers, ranging from tawny to white, forming a variable imperfect "V" on the back. The tail of most adults, which gives this species its name, is rufous brick-red above with a variably sized, black subterminal band and generally appears light buff-orange from below. In comparison, the typical pale immatures (i.e. less than two years old) typically have a mildly paler headed and tend to show a darker back than adults with more apparent pale wing-feather edges above (for descriptions of dark morph juveniles from B. j. calurus, which is also generally apt for description of rare dark morphs of other races, see under that subspecies description). In immature red-tailed hawks of all morphs, the tail is a light brown above with numerous small dark brown bars of roughly equal width, but these tend to be much broader on dark morph birds. Even in young red-tails, the tail may be a somewhat rufous tinge of brown. The bill is relatively short and dark, in the hooked shape characteristic of raptors, and the head can sometimes appear small in size against the thick body frame. The cere, the legs, and the feet of the red-tailed hawk are all yellow, as is the color of bare parts in many accipitrids of different lineages. 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, which is the adult eye-color in all races. Seen in flight, adults usually have dark brown along the lower edge of the wings, against a mostly pale wing, which bares light brownish barring. Individually, the underwing coverts can range from all dark to off-whitish (most often more heavily streaked with brown) which contrasts with a distinctive black patagium marking. The wing coloring of adults and immatures is similar but for typical pale morph immatures having somewhat heavier brownish markings.<p>Though the markings and color vary across the subspecies, the basic appearance of the red-tailed hawk is relatively consistent.<p>Overall, this species is blocky and broad in shape, often appearing (and being) heavier than other Buteos of similar length. They are the heaviest Buteos on average in eastern North America, albeit scarcely ahead of the larger winged rough-legged buzzard (Buteo lagopus), and second only in size in the west to the ferruginous hawk (Buteo regalis). Red-tailed hawks may be anywhere from the fifth to the ninth heaviest Buteo in the world depending on what figures are used. However, in the northwestern United States, ferruginous hawk females are 35% heavier than female red-tails from the same area. On average, western red-tailed hawks are relatively longer winged and lankier proportioned but are slightly less stocky, compact and heavy than eastern red-tailed hawks in North America. Eastern hawks may also have mildly larger talons and bills than western ones. Based on comparisons of morphology and function amongst all accipitrids, these features imply that western red-tails may need to vary their hunting more frequently to on the wing as the habitat diversifies to more open situations and presumably would hunt more variable and faster prey, whereas the birds of the east, which was historically well-wooded, are more dedicated perch hunters and can take somewhat larger prey but are likely more dedicated mammal hunters. In terms of size variation, red-tailed hawks run almost contrary to Bergmann's rule (i.e. that northern animals should be larger in relation than those closer to the Equator within a species) as one of the northernmost subspecies, B. j. alascensis, is the second smallest race based on linear dimensions and that two of the most southerly occurring races in the United States, B. j. fuertesi and B. j. umbrinus, respectively, are the largest proportioned of all red-tailed hawks. Red-tailed hawks tend have a relatively short but broad tails and thick, chunky wings. Although often described as long-winged, the proportional size of the wings is quite small and red-tails have high wing loading for a buteonine hawk. For comparison, two other widespread Buteo hawks in North America were found to weigh: 30 g (1.1 oz) for every square centimeter of wing area in the rough-legged buzzard (B. lagopus) and 44 g (1.6 oz)/cm2 in the red-shouldered hawk (B. lineatus). In contrast, the red-tailed hawk weighed considerably more for their wing area: 199 g (7.0 oz) per square cm.<p>As is the case with many raptors, the red-tailed hawk displays sexual dimorphism in size, as females are on average 25% larger than males. As is typical in large raptors, frequently reported mean body mass for red-tailed hawks is somewhat higher than expansive research reveals. Part of this weight variation is seasonal fluctuations; hawks tend to be heavier in winter than during migration or especially during the trying summer breeding season, and also due to clinal variation. Furthermore, immature hawks are usually lighter in mass than their adult counterparts despite having somewhat longer wings and tails. Male red-tailed hawks may weigh from 690 to 1,300 g (1.52 to 2.87 lb) and females may weigh 801 to 1,723 g (1.766 to 3.799 lb) (the lowest figure from a migrating female immature from Goshute Mountains, Nevada, the highest from a wintering female in Wisconsin). Some sources claim the largest females can weigh up to 2,000 g (4.4 lb), but whether this is in reference to wild hawks (as opposed to those in captivity or used for falconry) is not clear. The largest known survey of body mass in red-tailed hawks is still credited to Craighead and Craighead (1956), who found 100 males to average 1,028 g (2.266 lb) and 108 females to average 1,244 g (2.743 lb). However, these figures were apparently taken from labels on museum specimens, from natural history collections in Wisconsin and Pennsylvania, without note to the region, age, or subspecies of the specimens. However, 16 sources ranging in sample size from the aforementioned 208 specimens to only four hawks in Puerto Rico (with 9 of the 16 studies of migrating red-tails), showed that males weigh a mean of 860.2 g (1.896 lb) and females weigh a mean of 1,036.2 g (2.284 lb), about 15% lighter than prior species-wide published weights. Within the continental United States, typical weights of males can range from 840.8 g (1.854 lb) (for migrating males in Chelan County, Washington) to 1,031 g (2.273 lb) (for male hawks found dead in Massachusetts), and females ranged from 1,057.9 g (2.332 lb) (migrants in the Goshutes) to 1,373 g (3.027 lb) (for females diagnosed as B. j. borealis in western Kansas). Size variation in body mass reveals that the red-tailed hawk typically varies only a modest amount and that size differences are geographically inconsistent.<p>Male red-tailed hawks can measure 45 to 60 cm (18 to 24 in) in total length, females measuring 48 to 65 cm (19 to 26 in) long. Their wingspan typically can range from 105 to 141 cm (3 ft 5 in to 4 ft 8 in), although the largest females may possible span up to 147 cm (4 ft 10 in). 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) across the races. 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.<p>Although they overlap in range with most other American diurnal raptors, identifying most mature red-tailed hawks to species is relatively straightforward, particularly if viewing a typical adult at a reasonable distance. The red-tailed hawk is the only North American hawk with a rufous tail and a blackish patagium marking on the leading edge of its wing (which is obscured only on dark morph adults and Harlan's hawks by similarly dark-colored feathers). Other larger adult Buteo spp. in North America usually have obvious distinct markings that are absent in red-tails, whether the rufous-brown "beard" of Swainson's hawks (B. swainsonii) or the colorful rufous belly and shoulder markings and striking black-and-white mantle of red-shouldered hawks (also the small "windows" seen at the end of their primaries). In perched individuals, even as silhouettes, the shape of large Buteo spp. may be distinctive, such as the wingtips overhanging the tail in several other species, but not in red-tails. North American Buteo spp. range from the dainty, compact builds of much smaller ones, such as broad-winged hawk (B. platypterus) to the heavyset, neckless look of ferruginous hawks or the rough-legged buzzards, which have a compact, smaller appearance than a red-tail in perched birds due to its small bill, short neck, and much shorter tarsi, while the opposite effect occurs in flying rough-legs with their much bigger wing area. In flight, most other large North American Buteo spp. are distinctly longer and more slender-winged than red-tailed hawks, with the much paler ferruginous hawk having peculiarly slender wings in relation to its massive, chunky body. Swainson's hawks are distinctly darker on the wing and ferruginous hawks are much paler-winged than typical red-tailed hawks. Pale morph adult ferruginous hawk can show mildly tawny-pink (but never truly rufous) upper tail, and like red-tails tend to have dark markings on underwing-coverts and can have a dark belly band, but compared to red-tailed hawks have a distinctly broader head, their remiges are much whiter looking with very small, dark primary tips, they lack the red-tail's diagnostic patagial marks and usually also lack the dark subterminal tail-band, and ferruginous hawks have totally feathered tarsi. With its whitish head, the ferruginous hawk is most similar to Krider's red-tailed hawks, especially in immature plumage, but the larger hawk has broader head and narrower wing shape, and the ferruginous immatures are paler underneath and on their legs. Several species share a belly band with the typical red-tailed hawk, but they vary from subtle (as in the ferruginous hawk) to solid blackish, the latter in most light-morph rough-legged buzzards. More difficult to identify among adult red-tails are their darkest variations, as most species of Buteo in North America also have dark morphs. Western dark morph red-tails (i.e. B. j. calurus) adults, however, retain the typical distinctive brick-red tail, which other species lack, and may stand out even more against the otherwise all chocolate-brown to black bird. Standard pale juveniles when perched show a whitish patch in the outer half of the upper surface of the wing, which other juvenile Buteo spp. lack. The most difficult to identify stages and plumage types are dark morph juveniles, Harlan's hawk and some Krider's hawks (the latter mainly with typical ferruginous hawks as mentioned). Some darker juveniles are similar enough to other Buteo juveniles that they "cannot be identified to species with any confidence under various field conditions." However, field identification techniques have advanced in the last few decades and most experienced hawk-watchers can distinguish even the most vexingly plumaged immature hawks, especially as the wing shapes of each species becomes apparent after seeing many. Harlan's hawks are most similar to dark morph rough-legged buzzards and dark morph ferruginous hawks. Wing shape is the most reliable identification tool for distinguishing Harlan's hawks from these, but also the pale streaking on the breast of Harlan's, which tends to be conspicuous in most individuals, and is lacking in the other hawks. Also, dark morph ferruginous hawks do not have the dark subterminal band of a Harlan's hawk, but do bear a black undertail covert lacking in Harlan's.<p>The cry of the red-tailed hawk is a 2- to 3-second, hoarse, rasping scream, variously transcribed as kree-eee-ar, tsee-eeee-arrr or sheeeeee, 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 and most persistently in defiance 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, possibly as a warning sound. Nestlings may give peeping notes with a "soft, sleepy quality" that give way to occasional screams as they develop, but those are more likely to be a soft whistle rather than the harsh screams of the adults. Their latter hunger call, given from 11 days (as recorded in Alaska) to after fledgling (in California), is different, a two-syllabled, wailing klee-uk food cry exerted by the young when parents leave the nest or enter their field of vision. A strange mechanical sound "not very unlike the rush of distant water" has been reported as uttered in the midst of a sky-dance. A modified call of chirp-chwirk is given during courtship, while a low key, duck-like nasal gank may be given by pairs when they are relaxed.<p>The fierce, screaming cry of the adult 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. It is especially used in depictions of the bald eagle, which contributes to the common misconception that it is a bald eagle cry; actual bald eagle vocalizations are far softer and more chirpy than those of a red-tailed hawk.

Taxonomía

The red-tailed hawk was formally described in 1788 by German naturalist Johann Friedrich Gmelin under the binomial name Falco jamaicensis. Gmelin based his description on the "cream-coloured buzzard" described in 1781 by John Latham in his A General Synopsis of Birds. The type locality is Jamaica. The red-tailed hawk is now placed in the genus Buteo that was erected by French naturalist Bernard Germain de Lacépède in 1799.<p>The red-tailed hawk is a member of the subfamily Buteoninae, which includes about 55 currently recognized species. Unlike many lineages of accipitrids, which seemed to have radiated out of Africa or south Asia, the Buteoninae clearly originated in the Americas based on fossil records and current species distributions (more than 75% of the extant hawks from this lineage are found in the Americas). As a subfamily, the Buteoninae seem to be rather old based on genetic materials, with monophyletic genera bearing several million years of individual evolution. Diverse in plumage appearance, habitat, prey, and nesting preferences, buteonine hawks are nonetheless typically medium- to large-sized hawks with ample wings (while some fossil forms are very large, larger than any eagle alive today). The red-tailed hawk is a member of the genus Buteo, a group of medium-sized raptors with robust bodies and broad wings. Members of this genus are known as "buzzards" in Eurasia, but "hawks" in North America. Under current classification, the genus includes about 29 species, the second-most diverse of all extant accipitrid genera behind only Accipiter. The buzzards of Eurasia and Africa are mostly part of the genus Buteo, although two other small genera within the subfamily Buteoninae occur in Africa.<p>At one time, the rufous-tailed hawk (B. ventralis), distributed in Patagonia and some other areas of southern South America, was considered part of the red-tailed hawk species. With a massive distributional gap consisting of most of South America, the rufous-tailed hawk is considered a separate species now, but the two hawks still compromise a "species pair" or superspecies, as they are clearly closely related. The rufous-tailed hawk, while comparatively little studied, is very similar to the red-tailed hawk, being about the same size and possessing the same wing structure, and having more or less parallel nesting and hunting habits. Physically, however, rufous-tailed hawk adults do not attain a bright brick-red tail as do red-tailed hawks, instead retaining a dark brownish-cinnamon tail with many blackish crossbars similar to juvenile red-tailed hawks. Another, more well-known, close relative to the red-tailed hawk is the common buzzard (B. buteo), which has been considered as its Eurasian "broad ecological counterpart" and may also be within a species complex with red-tailed hawks. The common buzzard, in turn, is also part of a species complex with other Old World buzzards, namely the mountain buzzard (B. oreophilus), the forest buzzard (B. trizonatus ), and the Madagascar buzzard (B. brachypterus). All six species, although varying notably in size and plumage characteristics, in the alleged species complex that contains the red-tailed hawk share with it the feature of the blackish patagium marking, which is missing in most other Buteo spp.<p>At least 14 recognized subspecies of B. jamaicensis are described, which vary in range and in coloration. Not all authors accept every subspecies, though, particularly some of the insular races of the tropics (which differ only slightly in some cases from the nearest mainland forms) and particularly Krider's hawk, by far the most controversial red-tailed hawk race, as few authors agree on its suitability as a full-fledged subspecies.

Nombre científico

Buteo jamaicensis

Autoridad

(Gmelin, JF, 1788)

Orden

Accipitriformes

Familia

Accipitridae

Género

Buteo

Distribución y hábitat

The red-tailed hawk is one of the most widely distributed of all raptors in the Americas. It occupies the largest breeding range of any diurnal raptor north of the Mexican border, just ahead of the American kestrel (Falco sparverius). While the peregrine falcon (Falco peregrinus) has a greater latitudinal distribution as a nester in North America, its range as a breeding species is far more sporadic and sparse than that of red-tailed hawks. The red-tailed hawk breeds from nearly north-central Alaska, the Yukon, and a considerable portion of the Northwest Territories, there reaching as far as a breeder as Inuvik, Mackenzie River Delta and skirting the southern shores of Great Bear Lake and Great Slave Lake. Thereafter in northern Canada, breeding red-tails continue to northern Saskatchewan and across to north-central Ontario east to central Quebec and the Maritime Provinces of Canada, and south continuously to Florida. No substantial gaps occur throughout the entire contiguous United States where breeding red-tailed hawks do not occur. Along the Pacific, their range includes all of Baja California, including Islas Marías, and Socorro Island in the Revillagigedo Islands. On the mainland, breeding red-tails are found continuously to Oaxaca, then experience a brief gap at the Isthmus of Tehuantepec thereafter subsequently continuing from Chiapas through central Guatemala on to northern Nicaragua. To the south, the population in highlands from Costa Rica to central Panama is isolated from breeding birds in Nicaragua. Further east, breeding red-tailed hawks occur in the West Indies in north Bahamas (i.e. Grand Bahama, Abaco and Andros) and all larger islands (such as Cuba, Jamaica, Hispaniola, and Puerto Rico) and into the northern Lesser Antilles (Virgin Islands, Saint Barthélemy, Saba, Saint Kitts, and Nevis, being rare as a resident on Saint Eustatius and are probably extinct on Saint Martin). Their typical winter range stretches from southern Canada south throughout the remainder of the breeding range.<p>Red-tailed hawks have shown the ability to become habituated to almost any habitat present in North and Central America. Their preferred habitat is mixed forest and field, largely woodland edge with tall trees or alternately high bluffs that may be used as nesting and perching sites. They occupy a wide range of habitats and altitudes, including deserts, grasslands, nearly any coastal or wetland habitat, mountains, foothills, coniferous and deciduous woodlands, and tropical rainforests. Agricultural fields and pastures, which are more often than not varied with groves, ridges, or streamside trees in most parts of America, may make nearly ideal habitat for breeding or wintering red-tails. They also adapt well to suburban areas especially ones with tall trees or any kind of parkland.[excessive citations] Some red-tails may survive or even flourish in urban areas, usually hunting and roosting in available urban parks, cemeteries, road verges, and so on, and nesting freely either in trees or virtually any tall man-made structures. One famous urban red-tailed hawk, known as "Pale Male", became the subject of a nonfiction 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.[excessive citations] As studied in Syracuse, New York, the highway system has been very beneficial to red-tails as it juxtaposed trees and open areas and blocks human encroachment with fences, with the red-tailed hawks easily becoming acclimated to car traffic. The only practice that has a negative effect on the highway-occupying red-tails is the planting of exotic Phragmites, which may occasionally obscure otherwise ideal highway habitat.<p>In the northern Great Plains, the widespread practices of wildfire suppression and planting of exotic trees by humans has allowed groves of aspen and various other trees to invade what was once vast, almost continuous prairie grasslands, causing grassland obligates such as ferruginous hawks to decline and allowing parkland-favoring red-tails to flourish. To the contrary, clear-cutting of mature woodlands in New England, resulting in only fragmented and isolated stands of trees or low second growth remaining, was recorded to also benefit red-tailed hawks, despite being to the determent of breeding red-shouldered hawks. The red-tailed hawk, as a whole, rivals the peregrine falcon and the great horned owl among raptorial birds in the use of diverse habitats in North America. Beyond the high Arctic (as they discontinue as a breeder at the tree line), few other areas exist where red-tailed hawks are absent or rare in North and Central America. Some areas of unbroken forest, especially lowland tropical forests, rarely host red-tailed hawks, although they can occupy forested tropical highlands surprisingly well. In deserts, they can only occur where some variety of arborescent growth or ample rocky bluffs or canyons occur.

Migración

Migrantes completos

Comportamiento

Patrón migratorio: Migrantes completos.

Conservación

Tendencia poblacional: en aumento.

Tendencia poblacional

en aumento