Hawks Aloft, Inc.
Conservation, Avian Research, and Education
PO Box 10028 - Albuquerque, NM 87184 - (505) 828-9455

 

Swainson’s Hawk (Buteo swainsoni)

 Field Marks:

            - length: 20 in.  wingspan: 50 in.

            - dark flight feathers and pale wing lining

            - cream-colored breast with a dark head and chest bib in adults

            - uniformly brownish-gray back with lighter edges outlining each feather

Breeding Range:

This species breeds in the grasslands of the western United States from Texas to California, and between Canada and Mexico. 

Wintering Range:

During the non-breeding season, Swainson’s Hawks are gregarious and travel in flocks, called “kettles” containing hundreds to thousands of hawks.  They are a migratory species, and travel 6,200 miles to South America, concentrating mainly in Argentina.  The entire journey takes 2 weeks. 

Habitat Preferences:

The Swainson’s Hawk prefers to hunt in open or agricultural fields, where crops are no taller than native grasses.  They take advantage of field flooding, harvesting, and burning to flush prey.  When co-existing with Red-tailed Hawks, Swainson’s Hawks typically use smaller trees. 

Nesting:

They are usually monogamous, and remain together as long as both members of the pair live.  Swainson’s Hawks usually nest in solitary trees surrounded by open grassland or shrubland.  Males select the nest site, and both sexes build the nest in about one week.  Egg laying begins in April.  Eggs are incubated for approximately 35 days, and nestlings fledge about 43 days after hatching.  The young stay in the immediate area for 18-25 days after fledging, although they may remain dependent on their parents for up to 10 weeks after fledging. 

Feeding:

During the breeding season, Swainson’s Hawks are generalists, preying on ground squirrels, pocket gophers, voles, deer mice, and rabbits.  In New Mexico and Arizona, lizards and snakes are common prey items.  In late summer, and throughout fall and winter, Swainson’s Hawks are insectivorous, feeding almost exclusively on crickets, beetles, grasshoppers, and locusts.  In Argentina, Swainson’s Hawks are known as Locust Hawks. 

Conservation Status:

In the 1970’s, populations were estimated to be over 200,000.  In 1995, monocrotophos, an organophosphate used in South America to control insects, caused the mortality of approximately 6,000 Swainson’s Hawks.  As a result of this tragedy, increased education and monitoring has resulted in changes in pesticide use in these areas.  After this tragedy, Swainson’s Hawk populations are returneing to a steady and healthy level.  Although protected under the Migratory Bird Treaty Act, Swainson’s Hawks are not currently listed as threatened or endangered.