Identification

Perching: White or mottled abdomen, chocolate-colored bib, white chin, narrowly banded tail, and white spot ("flashlight") above beak. Back is uniformly dark.

Flying: Our only hawk with dark flight feathers (trailing part of wings) and light wing linings (front part of wings). Wings are narrow and pointed, held in a slight dihedral when soaring. Tail has several dark, narrow bands.

Nesting Habitat

Open country, usually grassland, on plains and in mountain valleys and parks. Large stick nest is usually placed in an isolated tree or shrub. They will nest in small trees in the medians of I-76 and I-70. One nest in the Pawnee National Grassland was only seven feet off the ground in a small cottonwood. These hawks are often seen circling behind farm machinery as they search for grasshoppers and other insects. They form kettles of several hundred birds in the fall, when they migrate to Argentina.

Nesting Dates

Courtship: early April to late June

Incubation: early April to late July

Dependent nestlings: early May to August

Incubation period is 33-36 days. The young fledge 38-46 days after hatching. Young remain with the adults until the whole family migrates south in September.

Statewide Distribution and Population

Nests virtually statewide below approximately 3000 m. Highest densities are on the northeastern plains, where these grassland specialists outnumber red-tailed hawks. Numbers appear to be declining in many areas, and insecticides have poisoned many thousands of birds on wintering grounds in Argentina.

State and Federal Status

Not listed.

Search and Nest Monitoring Protocol

Beginning in mid-April drive a set route, stopping every 500 m to scan all potential nest trees with binoculars. Repeat every two weeks throughout the nesting season. Monitor active nests at two-week intervals from a fixed observation point located at least 400 m from the nest.

Recommended Buffer Area

No foot traffic or recreational activity within 400 m of active nests or perches. These hawks will abandon nests if they are disturbed.

References

Bent, A. C. 1937. Life histories of North American birds of prey, part 1. U.S. National Museum Bulletin 167, Washington, D.C.

Fitzner, R. E. 1978. The ecology and behavior of the Swainson's hawk in southeastern Washington. Ph.D. dissertation, Washington State University, Pullman.

Johnsgard, P. A. 1990. Hawks, eagles, and falcons of North America. Smithsonian Institution press, Washington, D.C.

Kingery, H. E., ed. 1998. Colorado breeding bird atlas. Colorado Bird Atlas Partnership, Denver.

Olendorff, R. R. 1972. The large birds of prey of the Pawnee National Grassland: nesting habits and productivity. USIBP Technical Report 151, Fort Collins.

Wickersham, L.E. 2016. The Second Colorado Breeding Bird Atlas. Colorado Bird Atlas Partnership, Denver.