This week’s Bird of the Week, compliments of the Weminuche Audubon Society and Audubon Rockies, is the Swainson’s Hawk.
“Back in the day,” hearty family meals might be prepared in kettles. But, did you know that the term “kettle” applies to large groups of soaring hawks as well? The Swainson’s hawk is among those hawk species that migrate from their breeding grounds across the plains of Canada and the western U.S. to as far south as Argentina in “kettles” of hundreds or thousands of birds, one of the longest migrations of any American raptor. When not migrating, they may be spotted in open areas on various perches, or even hopping on the ground as they feed on small mammals or insects.
The Swainson’s hawk can be distinguished by having pointed wingtips with dark flight feathers on the trailing edge of their wings. The light-colored morph is shown in this week’s photo, but their most distinctive pattern reveals a dark-colored hood and rust-colored breast.
For nesting, they gather twigs, rope and similar debris to construct a nest in the tops of trees that are either solitary or in small groves. Their nests may be a couple of feet in diameter and a foot or so high. If other raptors dare to occupy an existing Swainson’s nest, the previous occupants may force the eviction of the newcomers. Laying one to five eggs per clutch, it will take 34 days or so for the eggs to hatch, and another three weeks or so before the fledglings leave the nest. During this time, the parents feed the young larger prey items, like small rodents, reptiles, etc. During the nonbreeding season, adults feed more commonly on smaller prey items, such as insects, although other, larger prey are always part of their diet.
Much of their historical plains habitat has been converted for agriculture, but they have adapted well and are often found in large groups following plows or harvesting equipment that flushes out their prey. Elimination of small woodlots and hedgerows by large-scale farming practices, along with pesticide use, however, represent potential challenges to their survival.