The autumn Broad-winged Hawk (Buteo platyperus) migration is an awe-inspiring event. Each September, vast numbers of these birds make their way from their breeding grounds in the deciduous forests to our north to their wintering grounds in Central and South America. This chunky, forest-dwelling hawk is our only raptor besides the Turkey Vulture that migrates in large flocks.

The broadwing is the smallest of the three buteos commonly found here (the other two are the Red-shouldered Hawk and the familiar Red-tailed Hawk). The small breeding population of broadwings in our area is relatively inconspicuous, spending much of the summer perched in the woods waiting for an unsuspecting small mammal, reptile, or amphibian to amble by. But during migration this bird really comes into its own.

Broad-winged Hawks migrate using vertical air currents called thermals, caused by differential heating of the Earth’s surface. Lifted by the rising air of the thermal, broadwings soar upward, sometimes thousands of feet. They ride the thermal as high as they can, and as it starts to weaken they glide down in a long stream to find the next thermal heading in the right direction to repeat the process. They can travel thousands of miles this way, expending very little energy.

In September 2011, Chestnut Ridge Hawkwatch saw one of the biggest Broad-winged Hawk migrations in many years. From 9 to 11am on September 17^th, 6,444 broadwings cruised by, and the total for the day was an astonishing 9,655. At about 14 ounces per bird, that’s around 4.2 tons of broadwings overhead! While numbers this large are not common, there are usually a few days each fall with more than a thousand broadwings at Chestnut Ridge. Your best bet for seeing this epic migration is from September 13^th to 26^th, when light northwest, north, or northeast winds are present a day or two after a cold front passes.