Montana Field Guide

Peregrine Falcon - Falco peregrinus

The Peregrine Falcon has long pointed wings, a dark crown and nape, and a dark wedge extending below the eye. The forehead is pale in immature birds, which are mainly brownish above rather than black or gray as in adults. Arctic birds are relatively pale, and the Peregrine Falcons of the northwest coast of North America are very dark, compared to the intermediate coloration of the subspecies (anatum) that once ranged across North America. They average 41 to 51 cm long and 91 to 112 cm in wingspan (NGS 1983).

Montana Range

Peregrine falcons arrive in northern breeding areas late April-early May; departure begins late August-early September. In the Bozeman area, observations in the 1950's and 1960's suggested migration periods around May 5 and September 15 (Skaar 1969).

Nests typically are situated on ledges of vertical cliffs, often with a sheltering overhang. Ideal locations include undisturbed areas with a wide view, near water, and close to plentiful prey. Substitute man-made sites can include tall buildings, bridges, rock quarries, and raised platforms.

In fall in the Bozeman area, birds have been seen following flocks of shore birds at the lakes (Skaar 1969).

Peregrine falcons feed primarily on birds (medium-size passerines up to small waterfowl). They have occassionally been reported to prey on small mammals (e.g., bats, lemmings), lizards, fishes, or insects (by young birds). Prey is pursued from a perch or while soaring. Peregrines may hunt up to several km from nest site (Skaggs et al. 1988). In general, much hunting occurs in morning, and to lesser extent toward evening, but may hunt anytime during day.

Nestlings have been reported in Montana from July 10 to 17 (Johnsgard 1986). The nesting period is estimated to be June and July (Davis 1961).

Clutch size averages 4 at mid-latitudes, and 3 in the far north. Incubation lasts 32-35 days, and is done mainly by female (the male brings food). Young birds fledge at 39-49 days, and gradually become independent. Brood losses are apparently caused mainly by bad weather, and lost clutches are usually replaced at alternate site.

Peregrine falcons first breed typically at 2-3 years of age, and occasionally as yearlings. They usually form a lifelong pair bond.

In some parts of Montana, Peregrine Falcons were considered fairly common in summer during the early 1900's (Skaar 1969). Post-war use of pesticides has been the main cause of the decline of these birds (Skaar pers. comm.). Great-horned owl may be a serious nest predator.