The flapping flight is relatively slow and direct. Wing beats have been calculated at 2.6 beats per second. In general, the Red-tailed Hawk flaps less than other buteos, except the Ferruginous Hawk. Ground speed has been estimated at about 40 miles per hour and air speed at 55 miles per hour (88 kilometers per hour). Soaring is a frequently-used flight strategy with the wings held, at times, in a slight dihedral. It is capable of holding motionless in the wind (kiting) with no wing beats. During migration, soaring has been reported to about 3,000 feet (4,800 kilometers) above ground. From an energy cost-benefit perspective, it has been suggested that soaring is not an efficient behavior for either hunting or thermoregulation. Other reasons for soaring include migration, exploration, territorial advertisement and courtship. Walking on the ground is slow and awkward but hopping when hunting is energetic.
Hunting strategies are versatile but may be grouped into the following 11 broad categories:
Perch and Wait
- this successful technique is used more than 80 percent of the time. Any elevated site may be used but, frequently trees, fence posts, power lines or other man-made structures are used.
Ground Pursuit
- hopping across the ground in pursuit of invertebrates is often seen in younger birds.
Flap or Glide
- maintaining an altitude of 200 feet (62 meters) or lower, the birds will quarter over the countryside much like a harrier. This style may be used closer to the ground as the hawks will dodge behind and between bushes, rocks or other obstacles to remain unseen as they approach prey.
Hovering
- using quickened wingbeats in order to maintain position, Redtails will survey the ground in search of prey.
Soaring
- it has been suggested that this is an inefficient, and ineffective, method for hunting, but stoops on potential prey are sometimes made from a high soar.
Cooperative Hunting
- mated pairs may close in on a quarry and cooperate on the kill.
Piracy - the Red-tailed Hawk has been seen robbing other raptors.
Aerial Foraging
- birds will occasionally sail in mid-air to catch large flying insects such as grasshoppers.
Accipiter Method
- often, in combination with the flap-glide flight, the Red-tailed Hawk will maneuver through stands of conifers in a goshawk-like manner.
Falcon Method
- the Red-tailed Hawk has been seen making fast stoops, like a falcon, specifically in pursuit of bats.
Carrion Eating
- the eating of freshly-killed animals is well-documented.
When swooping on prey, the wings are set into a glide pattern about 15 feet (4.7 meters) from the animal. At 10 feet (3.1 meters), the legs are extended and the final strike usually made with one foot farther ahead than the other. On impact, the bird then drops onto its "heels." The relative impact is less than that of large falcons, the Northern Goshawk or even the Cooper's Hawk. Small prey is carried to a feeding perch and may be swallowed whole. Birds are beheaded and plucked and larger mammals may be beheaded. If the prey is large, it may be partially dismembered and consumed before being taken to a feeding perch. Caching has been noted. Excess food not consumed at the nest is carried away. For the first four to five weeks, prey brought to the nest is torn into small pieces by the female before being given to the young. After this period, the nestlings tear apart their own food.
Inter-nest distances vary considerably and have been measured at slightly more than 0.5 miles (0.8 kilometers) to as much as 5 miles (8 kilometers) in one study area in Alaska. Territories may have common boundaries based upon interactions between adjacent pairs of birds. Buteos tend to have separate territories or if they do overlap with another species, behavioral routines are adjusted to minimize interactions. the Red-shouldered and Red-tailed Hawk are intolerant of each other and antagonistic with the Red-tailed Hawk being more dominant. The Red-tailed Hawk is also very antagonistic towards the Golden Eagle in California but little inter-action has been noted on other study sites. The hawk has shown aggression towards the Great Horned Owl but inter-nest distances between the two species have been recorded as close as 100 feet (31 meters). In a number of studies, where these two species attempted to nest in close proximity, the owl nests tended to be more successful. During the winter, the Red-tailed Hawk exhibits varying degrees of aggressive interaction towards each other, in attempts to maintain a winter territory. Behaviors vary from posturing, feather ruffling and eye contact through to full in-flight displays.
Most Red-tailed Hawks typically occur singly or in pairs, except during migration or around aggregated food supplies. Social interactions during these occasions seem to be minimal and the phenomena appear to be related to temporarily favorable environmental conditions as opposed to furthering social functions.
Nesting Red-tailed Hawks were shown to habituate to helicopter overflights with no apparent decrease in nesting success in one study. Other studies suggest that populations of Red-tails that have been exposed to human beings for long periods of time show less aggression towards human intruders than do populations that have had a shorter period of exposure.
The size of the home range varies with topography, habitat structure, season, disturbance and food availability. There may be consistent differences between males and females during the non-breeding seasons. In one Wisconsin study, the mean home ranges of males varied from a summer low of 292 acres (118 hectares) to a fall high of 975 acres (395 hectares). The mean sizes for females were considerably smaller except during the winter. Other studies have shown home ranges to vary from 600 to 1,150 acres (243 to 466 hectares). The home range is defended as a territory but defense intensity may decrease with distance from the nest.
Nesting densities have been recorded as low as one pair per 18 square miles (47 square kilometers) in sub-optimal Alaskan habitat to as high as one pair per 0.5 square miles (1.3 square kilometers) in California. The average has been suggested as one pair for every 2.2 square miles (5.7 square kilometers).
The pair-bond typically is lifelong monogamy. In non-migratory birds, the bond is maintained throughout the year. In the event of a lost mate, acquisition of a new partner can occur quickly and has occurred within one day. Courtship flights include high-circling, tilting and sky-dancing. Other territorial and or courtship behaviors include high-perching, whirling flight and boundary patrol flights.
"High-circling" has been seen in all seasons and may be a precursor to a number of activities. Birds rise high above the terrestrial territory and soar in wide circles, at times joined by other birds that may be from adjacent territories. This practice is an integral part of early phases in the breeding cycle and evolves into other flight activities that are preludes to copulation.
"Tilting" is performed by males in the spring and it may serve to reinforce the pair bond, although it does not seem to be performed on territory. With wings spread, tail partly spread, legs down and talons spread, the male circles slowly while tilting first one wing and then the other in a rocking motion. This position is maintained for some time and a female is always nearby.
The "sky dance" consists of a bird rising to a high altitude, pushing the wings forward and holding the tips in tightly then plunging in a steep dive at a high rate of speed. At the bottom of the plunge, the bird checks its speed and then shoots upward at about the same angle as the dive. This is repeated in series until the bird vanishes from sight. The purpose is to designate territorial boundaries and occurs before and well into the incubation period. Whether both sexes undertake the activity is not known.
While soaring fairly high, birds will suddenly "whirl" on one wing tip and rotate in a full circle. This may serve as territorial advertisement.
Mostly, copulation occurs when the female finishes a courtship flight and lands on a perch from which she will posture by holding her back in a horizontal position and fluttering her wings. The male lands on her back and copulates for a period of five to 12 seconds. Afterwards, the pair may perch quietly or perform aerial acrobatics. The frequency and span of time over which copulation may occur seems to be unrecorded.
The oldest known wild individual was 21.5 years old and a captive bird was known to have lived 29.5 years. The average mortality rate in the first year is about 54 percent and the mean annual mortality rate is about 20 percent after that. Only about 10 percent of hatchlings may be alive at age six and about 2 percent by age 13 years. Having reached age two, birds may be expected to live four to five more years. In order to maintain a stable population, it is estimated that each pair must produce between 1.33 to 1.38 young per breeding attempt.
Mortality is due to shooting, trapping, collision with automobiles, the accidental ingestion of lead shot, poisoning from rattlesnakes, starvation of nestlings, nest predation by owls and mammals, trampling of nestlings by the parents, death of nestlings due to flies and other parasites, nestling death due to exposure, falling from the nest, human interference near nests and various diseases. Pesticide contamination has been determined but it does not seem to be the cause of any significant reproductive failures.
ADAPTATIONS
The Red-tail Hawk is an adaptable predator that is able to change to a new prey base if one source of food declines. Its numbers are not tied to a particular combination of prey species.
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Migrates on long, broad wings
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