The Red-shouldered Hawk has a flight like that of an accipiter, with three to five quick wing beats followed by a glide. During the glide the wings are bowed downward. This species also soars with wings held flat and pressed forward. It does not hover.
The Red-shouldered Hawk is a diurnal hunter of the forest. Most hunting is done from a perch in the forest canopy from which it drops onto prey below. In one California study, all hunting attempts (over 250 began from a perch. Perch heights in Missouri ranged from 6.8 to 12.9 feet (2.1 to 4.0 m) above ground and included fences, hay piles, and trees. The Broad-winged Hawk also hunts from a perch, but usually one located at the edge of forest openings. The Red-shouldered Hawk drops onto small mammals within 290 feet (90 meters) of its perch. It also makes accipiter-like direct flights at birds attracted to bird feeders or watering places. It also courses like a Northern Harrier low over open ground to surprise its prey. It may also hunt small mammals, reptiles, and amphibians on foot, and may fly out of the forest to seize prey from the water's surface.
This species may occupy the same territory for life, although this needs more study. Pairs often use the same nest tree year after year. If disturbed a pair will change its nest site within the same territory. Home range size in eastern North America varies from 268 to 837 acres (109 to 339 hectares) during breeding season. Home ranges average smaller for females than males. The postbreeding home range is larger, with males again holding larger ranges. The male's home range usually includes all of the female's home range within his boundaries. Winter range size may be determined by the availability of food. The Red-shouldered Hawk is normally solitary or in pairs during breeding season. Even in migration it rarely forms flocks.
The Red-shouldered Hawk will defend its home range against Broad-winged Hawks, Red-tailed Hawks, Golden Eagles, Prairie Falcons, Barred Owls, and Great Horned Owls. Avian intruders near nests are chased and sometimes attacked. The Red-shouldered Hawk and the American Crow will attempt to rob each other and may jointly mob a Great Horned Owl in the hawk's territory. It is also known to rob Great Horned Owl nests. When a human is near a nest, the nesting bird may quietly leave or perch nearby and call. It may also circle, calling, overhead or even stoop at the person and attempt to strike. Aggression toward nest intruders increases from incubation through the nestling stage.
The courtship period may be as short as 18 days. The courtship display involves high-circling with both male and female circling with wings and tails wide spread. Both sexes call. They soar close to one another and then swing away. One may soar high and dive toward the other. The male also performs a sky-dance. He soars upward and calls. When the female appears, he dives steeply several times. Each dive is checked and followed by a wide spiral and a rapid ascent before the nest dive. In Massachusetts, migrant birds appeared to be paired when they arrived on territory. Copulation involves the female soliciting by crouching across a branch, drooping her wings and uttering a twittering call. The males performs the sky-dance with one of his dives taking him to the female's back. After copulation both birds may perch in the same tree.
The oldest Red-shouldered Hawk was a banded bird recovered at 19 years, 11 months. Average survival was 25.6 months for birds banded between 1955 and 1979. Locally, Great Horned Owl predation of nesting adults and/or their eggs and young can be quite heavy. In New York 33 percent of nine nests were lost to Great Horned Owls. In other areas, however, nest predation is not a major factor. Raccoons can also be nest predators. Other causes of mortality include trapping, shooting, and collision with vehicles. In California, the introduced grasses Bromus diandrus, B.rubens, Hordeum jubatum, and Avena barbata may become lodged in the eyes of Red-shouldered Hawks causing the birds to become blind and starve or collide with wires. Winter starvation of an immature has also been reported. Insecticides, including DDT and dieldrin, mercury, and other chemicals have been found in eggs and tissue, but eggshell thinning was less severe than for several other raptors. The relationship between chemical contamination and reproductive failure in the Red-shouldered Hawk remains unclear.
ADAPTATIONS
The Red-shouldered Hawks of southern California seem to have adapted much better to human development than this species has done elsewhere. It has adopted the introduced eucalyptus tree (various species) as a nesting tree and is often found in well forested residential areas.
Nesting Red-shouldered Hawks studied in Florida and California show an interesting adaptation between the size of prey brought to the nest and the distance from the nest the prey was caught. Small prey, like insects, are caught close to the nest tree while larger prey were brought in from both close and far distances. Such a strategy makes sense since the energy costs of transporting tiny prey from long distances could well exceed any benefits gained.
