The Broad-winged Hawk has been described as "tame" though the word "quiet" better describes its lifestyle as an inconspicuous hunt-and-perch predator. Human interference during nest building can cause adults to abandon the nest. However, once the nest is established the female Broad-winged Hawk can be aggressive toward intruders, even striking them. On most occasions, the incubating bird quietly leaves the nest when approached and perches nearby or circles overhead.
The Broad-winged Hawk uses the "sit" or "perch" and wait method of hunting, perching on a utility pole, wire or tree along a forest edge such as a forest roadcut, the shore of a creek or lake, or the edge of a clearing. The bird sights its prey on the ground, pushes off from its perch, and, after an initial series of rapid wing beats, typically glides until impact with the prey. It may mantle (stand with wings spread) over the prey for several minutes looking around before "footing" its prey. It may consume the prey on the ground or, as is typical for adults, carry it to a perch before feeding. Less common hunting methods include perching close (or even standing on the shore) to an amphibian breeding pond and seizing frogs as they breed, or cruising through the forest generally below tree-top level in a search for slow moving prey. Insects are also taken from a perch and in flight.
The pair bond may be long-term, though more study is needed. The members of a pair likely separate after breeding and do not reunite until returning to the breeding area. In one study, a pair from the previous season reunited within 0.3 miles (0.5 kilometers) of their former nesting home range. Adults appear to return to the same territory yearly, though they will nest in different parts of it from one breeding season to the next. The territory should contain forest, open areas, and a waterbody or wetland. Home range and territory size are not known. The species is generally solitary until migration when it commonly associates in flocks.
Broad-winged Hawks wintering in extreme southern Florida were often noisily harassed by American Kestrels trying, usually unsuccessfully, to evict the hawk from the kestrel's territory. The Broad-winged Hawk will defend its breeding territories against Red-tailed Hawks, Red-shouldered Hawks, and Northern Harriers. Occasionally, it will nest peacefully in proximity with another hawk's nest such as the Sharp-shinned Hawk, Cooper's Hawk, and Red-tailed Hawk.
Pair-formation and courtship displays are poorly known and apparently do not last very long as this species usually begins nest building and egg laying soon after spring arrival. High-circling is an advertising display that begins upon arrival at the breeding area. It involves one or two birds calling and circling over the forest. One bird may sideslip or dive downward upon another bird and almost make contact. The "sky-dance" involves a bird ascending in widening circles, calling, and soaring until nearly out of sight, then descending in long sweeps and curves. Also, other displays such as "tumbling", (the undulating-flight when a bird flies high undulating and the wings are flapped stiffly), and the "pigeon-flight" (which is characterized by deep wing beats followed by a glide with wings upheld in a V) have been described by other authors. The most common courtship vocalization is the two-noted whistle.
The oldest known wild bird lived 14 years and four months. Nests often fail due to predation. Half the nest failures in one New York study were due to predation by Great Horned Owls. Young Broad-winged Hawks suffer a high mortality rate; the average life expectancy in one study of 37 records was only one year. Hazards during migration include water crossings. Small numbers are found on the Dry Tortugas [tiny islands 60 miles (96 kilometers) west of Key West, Florida], each spring and, particularly, fall. Although capable of flight, these birds usually fail to find thermals that they could soar back to the mainland. Birds wintering in extreme southern Florida suffer significant mortality from collisions with automobiles.
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Although flocks of Broad-winged Hawks are seen during migration, the species has no real flock attachment and is free to follow its own flight plan. This behavioral characteristic enables Broad-winged Hawks to take advantage of local weather conditions to suit its own needs.
The Broad-winged Hawk's rufous and brown coloration acts as camouflage within its usual wooded environment.
This species may lay larger clutches in seasons of greater prey abundance as was shown in one western New York State study.
