<P> The 14 recognized subspecies vary in appearance and range, varying most often in color, and in the west of North America, red - tails are particularly often strongly polymorphic, with individuals ranging from almost white to nearly all black . The subspecies Harlan's hawk (B. j. harlani) is sometimes considered a separate species (B. harlani). The red - tailed hawk is one of the largest members of the genus Buteo, typically weighing from 690 to 1,600 g (1.5 to 3.5 lb) and measuring 45--65 cm (18--26 in) in length, with a wingspan from 110--141 cm (3 ft 7 in--4 ft 8 in). This species displays sexual dimorphism in size, with females averaging about 25% heavier than males . </P> <P> The diet of red - tailed hawks is highly variable and reflects their status as opportunistic generalist, but in North America, it is most often a predator of small mammals such as rodents . Prey that is terrestrial and diurnal is preferred so types such as ground squirrels are preferential where they naturally occur . Large numbers of birds and reptiles can occur in the diet in several areas and can even be the primary foods . Meanwhile, amphibians, fish and invertebrates can seem rare in the hawk's regular diet; however, they are not infrequently taken by immature hawks . Red - tailed hawks may survive on islands absent of native mammals on diets variously including invertebrates such as crabs, or lizards and birds . Like many Buteo, they hunt from a perch most often but can vary their hunting techniques where prey and habitat demand it . 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 . </P> <P> 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 of course 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 hues, 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 hue 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 hue, 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> <P> Though the markings and hue vary across the subspecies, the basic appearance of the red - tailed hawk is relatively consistent . 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 seventh 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 (Buteo lagopus) and 44 g (1.6 oz) per square cm in the red - shouldered hawk (Buteo lineatus). In contrast, the red - tailed hawk weighed considerably more for their wing area: 199 g (7.0 oz) per square cm . </P>

How much space does a red tailed hawk need