SPECIES

Red-tailed Hawk Buteo jamaicensis Scientific name definitions

C. R. Preston and R. D. Beane
Version: 1.0 — Published March 4, 2020
Text last updated May 20, 2009

Breeding

Phenology

Pair formation

In sedentary birds, mates remain together throughout the year (Petersen 1979a, Santana and Temple 1988). Whether this is typically the case in migratory birds is unknown. Aerial displays similar to those described above may be observed at any time of year (though much more common in early spring), and may serve to maintain pair bond outside of breeding season. Initial formation of a pair bond may occur during late winter or early spring.

Nest building

Usually begins late Feb or early Mar, but as early as late Dec in Arizona (Mader 1978) and late Jan in Wisconsin (Orians and Kuhlman 1956), and as late as mid-Apr in Alberta (Luttich et al. 1970).

First-only brood per season

One brood/season, but will renest when eggs fail to hatch, or nest destroyed. For most of interior North America, first eggs laid mid-late Mar; clutch typically completed 2–5 d after first egg laid. In Arizona, mean laying date 9 Mar over a period of 7 yr (25 Feb–2 Apr, n = 36) (Mader 1978), and in Puerto Rico first eggs laid in early Dec, peak egg-laying in Jan, but sometimes as late as late Apr (Santana and Temple 1988). In Alberta, mean date for initiation of incubation over a 4-year period was 1 May (12 Apr-26 May, n = 81) (Luttich et al. 1971). In a 2-yr study along the Colorado Front Range, the mean date of initiation of incubation was 28 Mar (18 Mar – 9 Apr, n = 10) (RDB). Mean clutch initiation dates in Wisconsin lag as the number of days with ≥10 cm of snow in Feb and Mar increase, apparently because fewer prey are available when snow cover is deep, and clutch initiation depends on female nutritional status (Petersen 1979a). Mean hatching date in a 4-yr study in Alberta ranged from 27 May – 5 June (Luttich et al. 1971). In Arizona, hatching from 25 Mar – 8 May in a 7-yr study (Mader 1978).

Nest Site

Selection process

Both members of a pair share in nest-site selection, but their respective roles are unknown. Typically, several nests from previous years are visited by both members of the pair. Two or more nests are often repaired, and greenery may be placed on these before a single nest is finally chosen (Bent 1937b).

Microhabitat

Nest typically located in mature forests of mixed conifer and deciduous trees adjacent to expansive openings, shrubland, grassland, or agricultural sites (Smith et al. 2003b). In tropics, nest sites span an elevational gradient from dry and moist lowlands to rainforest and cloud forest (Santana et al. 1986d). Site characteristics vary widely with vegetation and topography. In forested regions, nests are typically located in the crowns of tall trees within woodlots; occasionally in large tracts of unbroken forest. Nest tree is often high on a slope or taller than surrounding trees (Orians and Kuhlman 1956, Cornman 1973, Misztal 1974, Wiley 1975a, Petersen 1979a, Titus and Mosher 1981).

In Puerto Rico, Red-tails nest in trees typically taller than the mean canopy height of trees in surrounding plots, providing a view of at least half of the breeding territory (Santana et al. 1986d). Tree diameter, tree height, and maximum canopy width were significant characteristics of Red-tailed Hawk nests in oak woodlands of California (Tietje et al. 1997a) and Wyoming (Smith et al. 2003b). Tree species is probably unimportant to nest site selection, as long as the tree's growth, form, size, and location within the landscape provide accessibility and vigilance (Tietje et al. 1997a). In Puerto Rico, 49 nests were located among 21 different tree species (Santana et al. 1986d). Other important nest site characteristics include basal area of trees and distance to forest edge; a majority of nests occur in the top one-fourth of the tree (Tietje et al. 1997a, Smith et al. 2003b).

Where trees are scarce, Red-tails nest on cliffs, transmission line towers, windmills, trees (Bechard et al. 1990), and man-made structures projecting above the landscape (Stotz 1994, Brubaker et al. 20033,Pinel and Wallis 1972, Bechard et al. 1990); e.g., in New York City, the lintel above the window of a fourteenth-story apartment over-looking Central Park (Winn 1999). In a saguaro-palo verde (Carnegiea gigantea–Cercidium spp.) flatland in Arizona, saguaro used exclusively for nest sites (Mader 1978). Common characteristics of all sites include unobstructed access to nests from above and a commanding view of the adjacent environment. Red-tails typically choose sites taller and more open than sympatric Harris', Broad-winged, and Red-shouldered hawks (Mader 1978, Titus and Mosher 1981, Bednarz and Dinsmore 1982), and sites taller and closer to water than sympatric Ferruginous and Swainson's hawks (Smith 1971b, Schmutz et al. 1980, Coues 1874a, Bechard et al. 1990)

Nest

Construction

Both members of wild pair reported to build or refurbish nest within a few days, but the female spends more of her time forming the bowl (Bent 1937b, Fitch et al. 1946b, Orians and Kuhlman 1956, Austing 1964). Conifer sprigs may be placed on the outside of the structure early in the process (Bent 1937b), perhaps to advertise ownership. Most construction occurs in the morning and is completed within 4–7 d (Petersen 1979a). Sticks typically carried in the beak to the nest. Birds are very wary during this period and may discontinue nest-building if human presence is detected (Bent 1937b). In a captive pair, only the male constructed the nest, and the process extended for a longer period than reported in the wild (Kawata 1981).

Structure and composition matter

Body of nest usually constructed of deciduous sticks and twigs (1–2 cm diameter). Lining may include strips of bark, fresh green conifer, or deciduous sprigs, corn cobs, husks, stalks, aspen catkins, and other similar items (Bent 1937b, Bohm 1978, Petersen 1979a).

Dimensions

Typically 71–76 cm in outside diameter, with the inner bowl measuring 35–37 cm wide by 10–13 cm deep. Nests used and refurbished for several years may be somewhat larger. Bent (Bent 1937b) described one nest that measured > 96 cm in height.

Microclimate

Generally highly exposed in open canopy situations. A preponderance of nests in Ohio was oriented toward the south or west, presumably making them less vulnerable to strong northeasterly storm winds (Cornman 1973).

Maintenance or reuse of nests, alternate nests, nonbreeding nests

A nest may be used for ≥1 years by the same pair, vacated for ≥1 years, and used again. Refurbishment of previously built nests includes adding new sticks and twigs to reinforce outside and adding greenery, strips of bark, and other materials to line bowl. Sometimes ≥2 nests are built or refurbished without being used in a particular year (Bent 1937b,Janes 1984a).

Eggs

Shape

Elliptical to short subelliptical (Baicich and Harrison 2005).

Size

Length x breadth: borealis: 59.53 (55.61-62.15) x 47.49 (44.97-50.01), n = 20 clutches (49 eggs); calurus: 60.04 (55.57-68.25) x 47.10 (44.86-50.10), n = 20 (52); fuertesi: 59.42 (55.47-66.63) x 46.99 (43.37-49.61), n = 20 (46). Data from L. Kiff, Western Foundation Vert. Zool.

Color

“White, sometimes with a faint buffy wash; sparsely or heavily marked with blotches of buff, pale reddish-brown, dark brown, or purple. Markings often indistinct or combined with fine speckling” (Harrison 1979b9, Baicich and Harrison 2005).

Surface Texture

Smooth and non-glossy (Harrison 1979b, Baicich and Harrison 2005).

Eggshell thickness

Pre-1947, borealis: 0.438 (0.406-0.535) mm, n = 20 (49); calurus: 0.416 mm (0.364-0.453), n = 20 (52); fuertesi: 0.427 mm (0.389-0.484), n = 8 (19); umbrinus: 0.414 (0.353-0.460), n = 9 (23). There are few reports of post-1947 (post-DDT) eggshell thinning in Red-tailed Hawk populations (Anderson and Hickey 1972), and residue levels of DDT and other organochlorine contaminants in individuals and eggs have generally been low in this hawk (Henny et al. 1984a, Noble and Elliott 1990). This probably reflects the low exposure of Red-tails to such contaminants, since their diet is composed mostly of small mammals, which typically contain low levels of these compounds (Dustman and Stickel 1969).

Clutch size

Usually 2-3, sometimes 4 (Brown and Amadon 1968, Janes 1984b). See Demography and Populations, below.

Egg laying

Interval between nest selection and initiation of egg laying reportedly as short as 3 wk in Alberta (Luttich et al. 1971) and as long as 4–5 wk in Wisconsin (Orians and Kuhlman 1956). Typically, an egg is laid every other day, although a captive female laid the third egg 5 or 6 d after the second (Kawata 1981). If first clutch is removed or lost, a second is usually produced in another nest; rarely is a third laid (Bent 1937b). An unmated captive female laid 2 eggs 3 wk after an infertile clutch was removed from her nest (H. Meng in Palmer 1988f).

Incubation

Onset of incubation

Both parents incubate; begins with first egg laid. Incubation period variously estimated 28–35d (Bent 1937b, Hardy 1939).

Incubation patch

Single patch present in both sexes.

Incubation period

Incubation lasts for about 28 d; the male assists the female somewhat in this, brings food to her while she is incubating, and helps to feed young (Bent 1937b).

Parental behavior

In Wisconsin, female incubated all night and most of day; male incubated for about 1.5 h in mid-morning and again for up to 3 h in afternoon (Petersen 1979a). The male brought food to the incubating female, but she also hunted for herself. During the last week of the incubation period, the male's incubation declined to about ≤1.5 h per shift. Typically, the male provides most of the food for his mate during incubation, depending on his hunting ability and prey availability (e.g., Bent 1937b, Austing 1964, Wiley 1975a). In Alaska, adults were absent from eggs for periods of 15–30 min when food (snowshoe hare) availability was low; 8 of 10 nests failed (Lowe 1978).

Hatching

Hatching asynchronous; occurs over 2–4 d; little information available regarding the hatching process in wild individuals. In captivity, the first of three eggs laid hatched over a period of nearly 9 h (from pipping to nestling out of eggshell), the second hatched within 2 h after pipping, and the third hatched over a period of > 12 h (Kawata 1981). Captive parents began eating eggshells immediately after chicks hatched (Kawata 1981).

Young Birds

Condition at hatching

Altricial and nidicolous. Hatchlings unable to raise head; lie limp for first few hours after hatching (Fitch et al. 1946b, Kawata 1981).

Growth and development

General pattern of growth was sigmoid for several parameters (body mass and length of culmen, tarsus, third toe, and seventh primary) in male and 6 female nestlings in Ohio (Springer and Osborne 1983). Body mass averaged 58 g at hatching, with no difference between the sexes. Females reached a 16% higher asymptote (final nestling value) and grew for a longer time than males. Sexual dimorphism in mass became apparent at about 29 d.

Culmen length averaged 7.0 mm at hatching, and growth was essentially linear with age until day 25. Tarsus length averaged 20.5 mm at hatching and reached full nestling length in 28 d. Length of the third toe averaged 10.8 mm at hatching. No sexual dimorphism was evident in measurements or growth characteristics of culmen, tarsus, or third toe. The seventh primary emerged on day 9, and growth was essentially linear with age from day 12 to fledging.

Sexual dimorphism was apparent from the third week until fledging. Females reached an 8% higher asymptote than males. Generally, culmen, toes, and tarsus develop during the first 2 wk, whereas growth gains in body mass and primaries are fastest during weeks 3 and 4, respectively. Body mass is a good indicator of age up to the 24th d after hatching, and length of the seventh primary is the best indicator of age after day 24 (Fitch et al. 1946b, Springer and Osborne 1983). Petersen and Thompson (Petersen and Thompson 1977) and Bechard et al. (Bechard et al. 1985) have described techniques using the length of the fourth primary to age nestlings.

Behavior

Young active by second day; issue soft peeping calls, bounce, and wave continuously with their wings. By day 7, the bouncing and peeping begin to wane, and young peck at prey in nest. Nestlings emit high whistling notes (usually in response to adults overhead) by day 10, sit up on tarsometatarsi by day 15, become aggressive toward intruders by day 16, strike out with talons and wings by day 21, begin to stretch wings and exercise regularly by day 30, and leave the nest by day 46 (Fitch et al. 1946b). In captive birds, nestlings were raising heads and giving soft peeping calls toward parents within 12 h of hatching; actively begged for food within 18 h (Kawata 1981). Captive nestlings observed pecking and fighting with each other and self-preening 7 d after hatching, but aggression toward one another completely disappeared within 2 wk of hatching (Kawata 1981). By day 14, captive birds were head-bobbing, standing erect, and flapping and stretching wings, and were first observed to feed themselves on day 21.

Parental Care

Brooding

Typically, female parent broods from hatching until oldest nestling reaches 30–35 d of age. Young are preened during most brooding bouts. Time spent brooding may vary greatly daily and among nests, but generally ranges from about 1–5 h/d (CRP). In captive birds, brooding gradually decreased through the brooding period (Kawata 1981).

Feeding

The male provides most of the food for the female and their brood from hatching, although female may occasionally vacate the nest for brief hunts (Petersen 1979a). For the first 4–5 wk after hatching, prey is torn into small pieces for nestlings by the female; thereafter prey is deposited in the nest for nestlings to tear and eat (Fitch et al. 1946b).

In a captive pair (Kawata 1981), the female parent fed the young for the first time nearly 20 h after the first nestling emerged from the eggshell. In addition to feeding pieces of chicken and rat to her chicks, the female regurgitated a viscous fluid and fed it to receptive nestlings on 8 occasions in the first 5 d after hatching.

Generally, prey are delivered to nestlings 10–15 times/d from just before sunrise to just after sunset (e.g., Santana et al. 1986a). Delivery rate and prey biomass vary among individual birds and are affected by brood size and prey availability. In Alberta, McInvaille and Keith (Mcinvaille and Keith 1974) estimated that an average of 410 g/d and 730 g/d of food were brought to broods of 1 and 3 nestlings, respectively. An estimated 520 g/d adequately nourished the lone survivor of a brood in Washington (Stinson 1980b), and an average of 219 g (brood size of 1)–313 g (brood size of 2) of prey were brought daily to tethered young during a 5–yr study in Wisconsin (Petersen 1979a).

There is no evidence from wild pairs that parents adjust prey delivery as chicks age, and it is unclear how food is distributed between parents or among parents and chicks. In captive birds, the male parent played a more active role in feeding young as they aged, and the food was not deliberately distributed among the young by the parents. The rate of feeding was increased as chicks aged by supplying larger amounts of food per feeding session, rather than making more feeding sessions (Kawata 1981).

Developmental asynchrony among chicks (runting) and sibling aggression may occur when food is scarce. At a nest in Washington where food delivery was low and one chick was dominant to its nestmate, the female parent preferentially fed the dominant chick and frequently pecked the subordinate. There was violent sibling aggression in this nest, and the subordinate chick did not survive to fledging (Stinson 1980b). Young are generally fed the same foods as adults eat (Fitch et al. 1946b).

Weight loss by breeders probably varies with individual characteristics and environmental circumstances, but little information is available. At a nest in Arkansas, the female parent lost 98 g between hatching and 2 d before both young successfully fledged (CRP).

Early in the nestling period, adults typically remove unused prey from the nest within a day of deposition. In contrast, old carcasses may be allowed to accumulate in the nest late in the nestling period (Fitch et al. 1946b). In captive birds, nest attentiveness by parents gradually decreased during the nestling period, and the female parent was more aggressive than the male toward intruders (Kawata 1981).

Cooperative Breeding

Wiley (Wiley 1975b) reported 2 females and 1 male attending a nest with 4 nestlings in California. The male provided most of the food for the females to feed the young. In Wisconsin, Santana et al. (Santana et al. 1986a) recorded two females and one male tending a nest with one nestling. Both females defended the nest and fed, brooded, and preened the nestling. The male visited the nest and provided food to the females, but was not observed feeding the nestling.

Brood Parasitism by Other Species

Not known to occur.

Fledgling Stage

Young typically leave the nest for the first time about 42–46 d after hatching but usually stay very near the nest for the first few days after fledging. During this period, the fledglings remain fairly sedentary, though they may chase parents and beg for food. Parents deliver food directly or, more commonly, drop it near the young. Young may remain in the immediate vicinity of the nest for 18–25 d (Johnson 1973d, Petersen 1979a). Sustained flight is possible after about 2.5 wk post-fledging. After dispersing from the parental territory, juveniles from several nests may congregate and interact in a juvenile staging area.

During the first 3 wk after fledging, activity level doubles (Johnson 1973d, Johnson 1986c). Simple, perch-to-perch flight is most common (92% of all flights), and adults generally provide all vertebrate food. Young may supplement their vertebrate diet with insects and other invertebrates. Soaring flight begins near the end of this period. Prey-capture attempts, especially perch-to-ground forays, are common after 4 wk, but parents continue to provide most food (Johnson 1986c). Young may actively follow adults or remain sedentary, allowing parents to bring food to them (Petersen 1979a). Juvenile activity reaches a peak within 6 wk after leaving the nest. Johnson (1986) reported that juveniles obtained food from migrant adults and other juveniles, as well as parents, between 4–6 wk after fledging. Juveniles begin capturing small vertebrates 6–7 wk after fledging, but continue receiving food from parents for at least another week (Petersen 1979a, Johnson 1986c).

Immature Stage

In Montana, juvenile Red-tails remained associated with parents for up to 10 wk after fledging (migratory population; Johnson 1973d), and up to half a year after fledging in Wisconsin (resident population;Petersen 1979a). Immatures generally disperse from breeding areas and migrate earlier than adults (Geller and Temple 1983, but seeKessel and Springer 1966). Movements and behavior of immatures are poorly documented, but migratory immatures generally move further from breeding territory than adults do (Brinker and Erdman 1985). No substantial difference found in winter time-energy budgets between adults and immatures in Missouri (Diesel 1983). Orians (Orians 1955) reported a high percentage of immatures in urban (suboptimal) areas in Wisconsin, probably forced into suboptimal habitat by dominant adults.

Red-tailed Hawk Figure 6. Annual cycle of breeding, migration, and molt in the Red-tailed hawk
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Figure 6. Annual cycle of breeding, migration, and molt in the Red-tailed hawk

Annual cycle of breeding, migration, and molt in the Red-tailed hawk in the eastern U.S. Thick lines equal peak activity, thin lines off peak.

Red-tailed Hawk Red-tailed Hawk nest in saguaro cactus, central Arizona, April 1996.
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Red-tailed Hawk nest in saguaro cactus, central Arizona, April 1996.

; photographer Gerrit Vyn

Red-tailed Hawk Adult Female Red-tailed Hawk stripping bark for nest. NY City, March.
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Adult Female Red-tailed Hawk stripping bark for nest. NY City, March.

, Mar 14, 2004; photographer Cal Vornberger

Red-tailed Hawk Adult female Red-tailed Hawk nest building; NY City, May.
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Adult female Red-tailed Hawk nest building; NY City, May.

This chick was blown up and out of its nest by a sudden updraft, still clutching part of the nest when the wind carried him upwards., May 29, 2004; photographer Cal Vornberger

Red-tailed Hawk Adult Red-tailed Hawk adult at nest with chicks. Cochrane, Alberta, June.
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Adult Red-tailed Hawk adult at nest with chicks. Cochrane, Alberta, June.

The following link is to this contributor's Flickr stream or website. http://www.flickr.com/photos/mama_lumen/, Jun 29, 2008; photographer gnude2000

Red-tailed Hawk Red-tailed Hawk nestling, St. John the Divine, NYC, May.
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Red-tailed Hawk nestling, St. John the Divine, NYC, May.

The following link is to this contributor's Flickr stream or website. http://www.flickr.com/photos/rbs10025/, May 31, 2007; photographer Robert Schmunk

Recommended Citation

Preston, C. R. and R. D. Beane (2020). Red-tailed Hawk (Buteo jamaicensis), version 1.0. In Birds of the World (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.rethaw.01