The species tends to congregate in winter. Voice is a weak nasal pee, pee, pee. Marsh hawks nest on or near the ground, sometimes in fields and occasionally on a branch over the water. Nests are made of sticks, straw, grasses and are lined with feathers. Incubation is mostly by the female and takes about 24 days.
Young birds are browner and heavily streaked below.
Peregrines have long pointed wings and fly with quick rowing wingbeats similar to those of a pigeon. When the prey falls to the ground, the falcon picks it up and carries it to a convenient perch to be eaten. The peregrine was near extinction and is on the federal Endangered Species List. Persistent highly toxic pesticides, which affect peregrine reproduction, nearly eliminated the bird in the eastern United States. Cornell University ornithologists pioneered the restoration of this species, raising peregrines from captive parents and releasing the young birds in suitable habitat.