39. Swainson's Hawk

Nests - Initiation of pair-bonding begins upon return to breeding grounds, Apr in colder part of range but early Mar in central California. Both members of pair participate in nest initiation. Once the site is determined, nest-building is usually completed in about 1 wk but occasionally takes ≤2 wk. Typically a solitary tree, bush, small grove, or line of trees along stream course. Typical nest trees include willows, black locusts (Robinia pseudoacacia), box elders (Acer negundo), junipers (Juniperus spp.), oaks (Quercus spp.), aspens, and cottonwoods. Typical raptor nest: bulky, unsightly mass of sticks. Constructed of various freshly broken sticks, twigs, and debris.

Eggs - Short subelliptical to elliptical. off-white or nearly so; others irregularly or sparsely marked with dark reddish brown or pale purplish blotches around larger end. Clutch size typically 1 to 4 eggs.

Incubation - 34–35 days and female does nearly all incubation. Male covers eggs only while female feeds away from nest for brief periods during day.

Fledging - Young first exercise wings when 29–33 d old. Young quickly adapt to branches and then spend little time on nest. First flight at 38–46 d. For first 7–10 d after first flight, young stay near nest and fly only to chase adults carrying prey.