Broad-winged Hawks are Hawk Mountain's most numerous species.

The Broad-winged Hawk is one of only five North American raptors that are complete migrants. All continental populations of broadwings are migratory, the five West Indian subspecies are sedentary. Most Broad-winged Hawks breeding in the eastern United States and southeastern Canada migrate to wintering grounds in southern Central America and central South America. A small portion of the population, consisting mainly of juveniles, winters in Florida, coastal Texas, and in the lower Mississippi Delta. Little is known regarding the habitats used by broadwings during migration, but they appear to roost only in wooded areas. On their wintering grounds in Central and South America, Broad-winged Hawks inhabit a range of woodland types including mature tropical forests, second-growth forests, forest edges, and associated clearings. 

 To reduce the energy costs associated with long distance migration, this migrant capitalizes on favorable atmospheric conditions such as mountain updrafts and thermals for soaring. By allowing themselves to be drifted by prevailing winds, migrating broadwings are able to reduce energy costs and fly faster. Even so migrants need to balance between the energy-saving benefits of flying in the direction of the prevailing winds, while still maintaining a direct path to their destination. At the beginning of their migration, migrants make less of an effort to correct for wind drift, but as they get closer to their destination compensatory movements increase. Prevailing wind conditions in eastern North America push southbound birds to the south and east of their return routes in the spring, creating an elliptical migration route. Thus, watchsites along the Atlantic coast and the Kittatinny Ridge in eastern Pennsylvania observe far fewer broadwings in the spring than in the fall. In the spring, large counts are observed at inland sites, such as those on Lake Ontario, including Derby Hill, New York and Braddock Bay, New York. 

 Broad-winged Hawks often soar in thermals and mountain updrafts. Like other raptors, Broad-winged Hawks begin their migration as broad-frontal migrants but then concentrate along leading lines. Soaring migrants like Broad-winged Hawks avoid large water crossings. Favorable landscape features that concentrate migrants include ridges where conditions are suitable for slope soaring, and manmade features such as cities where strong thermals form. Since thermal soaring functions as their primary migration strategy, Broad-winged Hawks do not exhibit strong ridge adherence.

 Unlike most North American raptors, broadwings migrate in large flocks called “kettles,” that range in size from several birds to thousands of individuals. Only a small percentage of broadwings migrate alone. Broadwings are not particularly social, but flocking increases their ability to find thermals and mountain updrafts. For Broad-winged Hawks one of the best means of locating thermals is by following another Broad-winged Hawk. In addition to facilitating an individual’s ability to efficiently find thermals, flocking is also believed to aid in orientation and navigation. Observations at Hawk Mountain Sanctuary indicate that adult Broad-winged Hawks are more likely to flock than are juveniles, and that in mixed-aged flocks adults are more likely to be the leading bird or in the leading half of the flock. By flocking and following more experienced adults, juveniles maximize the extent to which they take advantage of favorable atmospheric conditions and reduce the extent to which they fly off course. Observations of juveniles wintering in Florida, a location off the migration route and north of the typical wintering grounds, appears to support the idea that juveniles are more likely than adults to have difficulty with navigation and orientation. 

 The need to migrate using thermals also plays a role in the timing of Broad-winged Hawk migration. The Broad-winged Hawk is one of the first migrants to leave their breeding grounds in the fall and one of the last to return in the spring. In autumn at Hawk Mountain, 95% of the migrating Broad-winged Hawks sighted pass through during a two-week period in mid-September. In the past, researchers attributed the Broad-winged Hawk’s early departure from its breeding ground to the long distance they need to travel to their wintering grounds or to the reduced availability of their preferred prey on their breeding grounds. Analysis of 60 years of Hawk Mountain Sanctuary data suggests that the timing and concentration of Broad-winged Hawk migration are neither a consequence of long distance movements nor food availability. Rather, the early and compressed fall migration is a result of the Broadwinged Hawk’s dependence on thermals. Broad-winged Hawks need to leave their nesting grounds as soon as possible in order to migrate when thermal activity is most predictable. Birds that leave later in the season, when the days are shorter and the sun is not as high in the sky, will face conditions that are less favorable for thermal migration. When thermal production is reduced, migrants must resort to powered flight to a greater extent, an energetically costly and undesirable alternative. Their hurried departure from North America in mid- to late September enables them to avoid such problems.