Montana Field Guide

Sexes are similar in color, uniformly buffy brown above and creamy white below. The tail is rufous-brown with very fine barring. Adults have a brown-barred breast and belly, while juveniles have more boldly brown-streaked under-parts. Both adults and young have dark brown feathers on the undersides of the wings near the body ("wing pits"), and a dark brown stripe running diagonally backward from below the eye. The eye is dark brown. Males average about 15 inches in length and have a wingspan of about 37 inches in length, and females average about 17 inches in length with a wingspan of about 41 inches (FWP). A medium-sized falcon with pointed wings, a hooked bill, and conspicuous (in flight) dark patches near the body on the underside of the wings (axillaries and coverts); adults are pale brown above, whitish with heavy spotting below; head has narrow dark streak extending downward from each eye; immatures are buffy below; average length 39-50 cm, wingspan 89-109 cm (NGS 1983).

Prairie falcons are about the same size as juvenile peregrine falcons, but lighter in color. they are much smaller than gyrfalcons, and much larger than female merlins. none of the other falcons have the dark "wing pits" under the wings (fwp). differs from all other north american falcons in having dark patches in the wingpits. paler above than peregrine falcon (falco peregrinus) and merlin (falco columbarius). lacks the heavy dark wedge on the side of the face of the peregrine falcon.

Migration southward and eastward from Montana nesting areas is common (FWP). Bozeman area: wintering birds arrive 11/1-11/15 and leave by 3/25 (Skaar 1969).

Prairie falcons use cliffs for nesting, and grassland and prairie habitats for hunting (FWP). 83% nesting territories located between 4000-6000 ft. Most nests are on cliffs avg. 125' ht. Mean ht. above base of cliff was 80'. 72% of eyries faced S or E. Almost all nests overlooked at least some grassland (Leedy 1972).

Prairie falcons feed primarily on birds and mammals, often exploiting locally abundant prey populations. In Montana, common prey are western meadowlarks, horned larks, and ground squirrels (FWP). W MT: Richardson's ground squirrels (CITELLUS RICHARDSONII) and horned larks (EREMOPHILIA ALPESTRIS) were most common prey at eyries, with western meadowlarks (STORNELLA NEGLECTA) next in abundance (Leedy 1972).

Nests sites are on cliffs, usually in a large hole or sheltered ledge, or sometimes in stick nests built by golden eagles or hawks. Adults establish nesting territories in late March or early April, and noisy aerial courtship displays are common. Clutches of three to five eggs are usually laid in late April, and incubated for about one month. Young leave the nest when about 40 days old, but may stay nearby for up to four weeks afterward (FWP). Pairing occurred 4/1; completion of clutches 4/10-5/14; hatching 5/9-6/12; fledging 6/15-7/21. Mean #'s: eggs/clutch 4.3; fledglings/success. pr. 2.9; fledglings/territory 1.9; young fledged/nesting attempt 0.9 (Leedy 1972).