The Broad-winged Hawk is a small, stocky buteo with broad white-and-black tail bands. It is a common breeder in deciduous or mixed-deciduous forests throughout eastern North America and into parts of central Canada. Interestingly enough, the Genus name Buteo translates from the Latin for buzzard, and the entire scientific name roughly translates to mean ‘a broad-winged buzzard’. These hawks migrate south in the fall in large flocks called "kettles", often mixed with falcons and accipiter hawks. Certain aspects of the Broad-winged Hawk’s migration behavior and breeding ecology has been well-documented, but little is known about the wintering habitats and other facets of its life history.
History and Status
This hawk is a breeder throughout the state, but is most common in the mountains. It is a neotropical migrant, although small numbers of immature birds winter in south Florida and the Florida Keys. Neotropical (New World) migratory birds breed during our summer in temperate North America, migrating north each spring from wintering areas, then fly back south to spend the bulk of our year in Mexico, Central or South America, or the Caribbean.
Nesting mostly in forested habitat with broad-leaf and coniferous trees, it will use younger forests with more openings than the resident Red-shouldered Hawk. This species also often hunts forest edges though it tends to nest away from human dwellings. Conifer plantations are rarely used as nest sites. Migrants usually roost in wooded areas, while on the wintering grounds birds tolerate a variety of forest types from mature forest to second-growth, as well as edges and open areas.
The Breeding Bird Survey (BBS) typically detects low numbers of this bird per route and is likely inadequate for surveying the species. Small sample sizes for BBS routes in southern states impede accurate assessment of trends, although most states estimate stable populations as of 1989. Analysis of BBS data from North Carolina from 1966-1994 indicate a slight increasing trend for populations of this bird. Migration counts at northeastern sites such as Hawk Mountain, Pa. show a stable trend from 1936-1986, but counts from the 1990’s suggest a possible decline in some eastern populations, or a change in migration routes. It is unclear if a drop in migration numbers represents a population trend or a change in migration patterns in the east. Although forested habitat seems to be increasing in some areas of the east, the increase in forest maturity and the level of fragmentation may be influencing the quality of breeding areas for this hawk.
Description
Sexes are similar in plumage, but females are slightly larger and heavier. Two color morphs exist, but the adult light color morph is the one almost always found during the breeding season in our state. Typically the back is brownish with cinnamon or chestnut barring below, and a whitish throat. The tail is black with one prominent whitish band across the middle, a less visible narrower band near the base of the tail and a narrow white band along the edge. There is a prominent black band along the trailing edge of the undersurface of the wing. Juveniles are similar to adults, but the underparts are white with longitudinal brownish streaks on the breast and there is often more streaking on the sides and belly. The tail of younger birds is buffy colored with narrow dark brown bands.
The adult Red-shouldered Hawk is somewhat similar, but Red-shouldered Hawks are bigger and have rufous shoulders, longer legs and more white bands on the tail. In flight, Red-shouldered Hawks also appear to hold its wings stretched forward and not flat and perpendicular to the body as in the Broad-winged Hawk. The Red-tailed Hawk is a much larger bird with a clear white breast and ventral streaking across the abdomen. The voice of the Broad-winged Hawk is a high pitched whistle (peee-uurr) that is very different than screams of the Red-tailed and Red-shouldered Hawks during the breeding season.
Habitat and Habits
This species is secretive while nesting but conspicuous during spring and fall migrations. Nesting pairs spend most of their time beneath the forest canopy, perch-hunting for a variety of small animals. The territorial adults can be located by their plaintive whistle that is often given during occasional soaring flights above the canopy. The adults usually pair quickly on the breeding grounds, but are much more solitary on the wintering areas. Nest building may take a month, but some pairs may reuse nests in subsequent years or renovate the nests of other species. Pairs will actively defend home ranges from other Broad-wings and usually react aggressively to Red-tailed Hawks and Red-shouldered Hawks. These hawks usually nest in deciduous or mixed deciduous-coniferous forests, and nests are built in a wide variety of tree species. In the south oaks are often used. Both sexes help construct the nest, although the female usually does most of the work. The females do most of the incubating while the males provide most of the food. The female does all the feeding of the young, with the male bringing prey to her away from the nest or dropping it on the nest if the female is away. In most areas, mammals are the main prey brought to the young. These hawks will also catch a wide variety of other small animals such as insects, amphibians, reptiles and birds. Their diet will usually depend on local availability of prey. On average this hawk takes much smaller prey than Red-tailed Hawks. Wintering Broad-winged Hawks feed on large insects, snakes, lizards, frogs, crabs and small mammals, and less frequently on birds. The Broad-winged Hawk is one of five North American diurnal birds of prey that are complete migrants. Continental populations vacate their breeding range in winter, but the endemic Caribbean subspecies are residents. This hawk generally migrates in large flocks ranging from tens to thousands. They frequently soar on thermals and rarely resort to flapping flight. It has been suggested that they use an elliptical migration path to compensate for prevailing winds in spring and fall. Although the migration period at any one site in spring and fall may last around two months, most individuals pass during a brief and concentrated two week period during both seasons. The peak of fall movements usually are during the last part of September in our mountains.
Range and Distribution
In North America, they breed from central Alberta eastward across lower Canada and throughout the eastern half of the United States. There is a year-round population in the Caribbean. Winter residents occur in Mexico along the Pacific slope, throughout middle America and In south America south to Peru, Bolivia, Columbia, Venezuela and Brazil. They also winter occasionally in south Florida, and there has been an increase in winter record reports in the southern United States since the 1950’s. Oldest recovered bird was 14 years, but few are banded.
People Interactions
Early in the twentieth century, enough birds were shot during migration and during the breeding season to likely impact this species. More recently, habitat alteration, fragmentation, and elimination (especially on the wintering grounds), may pose a more serious threat. On its wintering range it is still viewed widely as a pest and protective laws are not enforced against illegal shooters. Recent continued use of the pesticide DDT south of the United States may effect some birds that have a high component of insects in their diet. In the Florida Keys, many young wintering birds are killed by vehicles. While reforestation of many eastern areas in the United States has increased potential breeding habitat for this species, forest area on the wintering range may have decreased by over 120,000 acres. This hawk appears to select larger trees for nesting, often with small clearings and water nearby. Breeding birds seem to use mostly large areas of forest, but may be more tolerant of silviculture than other woodland raptors. Preservation of forest patches for roosting along major flyways may be vital for this and other long-distance migrants.
Suggested Reading
Kaufman, Ken. Lives of North American Birds. Houghton Mifflin Company, 1996.
Terres, J. K. The Audubon Society Encyclopedia of North American Birds. Knopf Publishers, 1980.