The flight of the Ferruginous Hawk is active, with slow wing beats much like that of a small eagle. Soaring with the wings held in a strong dihedral has been noted, as well as gliding with the wings held flat, or in a modified dihedral. Hovering and low cruising over the ground are also used as hunting techniques. The wing beat has been described as "fluid" by some observers.
Hunting may occur at any time of the day depending upon the activity patterns of the major prey species. A bimodal pattern of early morning and late afternoon hunting may be common. The hunting tactics can be grouped into seven basic strategies:
Perch and Wait
- perching is on any elevated site, natural or man-made
Ground Perching
- the hawk will stand on the ground at a rodent burrow after initially locating it from the air. As the burrowing animal reaches the surface, the hawk rises into the air and pounces upon it even while it is still underneath the loose earth.
Low-level Flight
- birds will course over the landscape within a few yards of the ground and pursue in direct, low level chases, or they will hunt from 40 to 60 feet (12.4 to 18.6 meters) above the ground.
High-level Flight
- birds will hunt while soaring, but the success rate is generally low.
Hovering
- using quickened wing beats, often in times of increased winds, the birds will search the ground and drop on the prey.
Cooperative Hunting
- mates have been known to assist each other.
Piracy
- the Ferruginous Hawk has been observed gathering around a hunter shooting prairie dogs, and to claim shot "dogs" by flying to them and mantling over them.
In the strike, kill, and consumption type of predation, the victims are seized with the feet and a series of blows may be meted out, including driving the rear talon into the body to puncture vital organs. Biting with the beak may also take place. Before bringing prey to the nest, the adults will often eat the head. At the nest, birds are plucked and mammals torn into pieces before being fed to the young. Food caching has been noted, but not generally near the nest.
The Ferruginous Hawk maintains minimum distances from other nesting raptors but will nest closer than necessary, suggesting that the distance is not fixed. The "nearest neighbor" distance has varied from less than 1 mile (1.6 kilometers) to as much as 4 miles (6.4 kilometers) with an average of 2 miles (3.2 kilometers). Nests facing different hunting territories are tolerated much closer than nests facing the same hunting territory. The minimum distance between nests is probably about one half mile on densely-occupied areas. Territorial conflicts have been reported with other species, such as the Great Horned and Short-eared )Owl, Northern Harrier, Red-tailed and Swainson's Hawk, Golden Eagle, accipiters, ravens, and magpies. It seems to be quite tolerant of other Ferruginous Hawks from adjacent territories.
Nesting densities in several studies have varied from one pair per four to 2,450 square miles (10.4 to 6,346 square kilometers). In Alberta, on one study site, there was a stable density of one pair per four square miles (10.4 square kilometers), on average with little deviation from this mean. In Idaho, the average home range for four pairs of Ferruginous Hawks in the Snake River area was slightly over two square miles (5.2 square kilometers).
Courtship flights seem to be limited in the accepted sense. Both sexes engage in high, circling flight but literature details are sketchy. Soaring activities may primarily be variations on territorial defense flights as opposed to courtship per se. The "flutter - glide" flight consists of a series of shallow, rapid wing beats interspersed with brief glides and may serve to advertise the territory. The "sky-dance" is stimulated by an intruder and consists of slow flight with deep, labored wing beats with irregular yawing and pitching that may terminate in steep dives. In the "follow-soar" maneuver, the male Ferruginous Hawk will fly below an intruder and escort it out of the territory. High perching occurs from prominent places around the nest, particularly early in the breeding cycle. Aggressive actions such as attacking, talon-grasping, and pursuit have been noted by some observers. Copulation begins before construction of the new nest, and increases in frequency until the start of egg laying. The passing of food may occur before the activity. The duration of copulation is from four to 18 seconds.
Birds have been known to live for 20 years in the wild, but most birds probably die within the first five years. The oldest banded birds were recovered at age 20. First year mortality has been estimated at 66 percent and the adult mortality at 25 percent. The reasons for mortality include illegal shooting, loss of a satisfactory food supply, harassment, predation, and starvation of nestlings during times of low food supply. Ground nests are susceptible to predation by coyotes, and nestlings may be preyed upon by Great Horned Owls and Golden Eagles.
ADAPTATIONS
The Ferruginous Hawk is one of the most adaptable nesters of all of the raptors, and will use trees, ledges, rock or dirt outcrops, the ground, haystacks, nest platforms, power poles, and other man-made structures. Pairs have a high reproductive potential, thus allowing a rapid recovery of populations in response to upswings in the prey base.
