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Birds of the St. Croix River Valley: Minnesota and Wisconsin

FAMILY FALCONIDAE

Falcons


Gyrfalcon -- Peregrine Falcon -- Merlin -- American Kestrel

Gyrfalcon (Falco rusticolus)

Status: Accidental, one record.

Record: One was observed near Marine-on-St. Croix, Washington County on 24 December 1973 (Honetschlager 1974).


Peregrine Falcon (Falco peregrinus)

Status: Regular migrant and former nesting species. The U.S. Fish and Wildlife Service and WDNR (Les 1979) have listed this species as endangered. Pesticides, habitat loss, and human harassment are among the major causes of the decline.

Migration: Rare migrant throughout the Valley. Spring migrants arrive in the Western Upland 10-15 April (earliest-4 April 1974, Pierce County) and the Northern Highland 15-20 April. Departure from the Valley occurs 15-20 May. Fall migrants arrive 5-10 September and most observations occur during 15-30 September and departure by 15 October. During fall migration, the restored prairie on the refuge portion of Crex Meadows is the most consistent area in the Valley to observe this raptor.

Nesting Season Distribution: Formerly a rare and local nesting bird along the St. Croix River. Roberts (1932) reported that fewer than six pairs nested along the upper St. Croix River in the late 1920's. Surber (1919) reported a pair of peregrine falcons along the St. Croix River near the mouth of the Tamarack River (Pine County) during July 1918. Jackson (1941) did not report this species during the 1919 nesting season in northwestern Wisconsin. Apparently the last known nesting attempt occurred along "the upper St. Croix River" in 1945 (Green and Janssen 1975).

Habitat: Roberts' (1932) description of peregrine falcons nesting "along the bluffs" of the St. Croix River is all that is known of their nesting habitat in the Valley. Peregrine falcons presumably nested on the relatively inaccessible rock ledges on the sides of the steepest bluffs. During migration, most peregrine falcons are observed in association with mudflats on large natural and man-made wetlands. Open mudflats support migrant shorebirds and waterfowl and provide excellent hunting for falcons.


Merlin (Falco columbarius)

Status: Regular migrant and casual summer resident.

Migration: Rare migrant throughout the Valley. Spring migrants arrive in the Western Upland about 5-10 April and the Northern Highland 10-15 April. During spring migration the merlin is most frequently observed 1-15 May and departs by 25 May (latest-28 May 1977, St. Croix County). Fall migrants arrive 25 August to 5 September and are most frequently observed 10-25 September. Departure from the Northern Highland occurs 1-10 October and elsewhere by 20 October.

Nesting Season Distribution: Casual summer resident, restricted to the Northern Highland. Jackson (1941) mentioned the observation of an adult at Gordon (Douglas County) on 28 July 1919. I observed an adult merlin near Moose Junction (Douglas County, Sec. 14, T. 44 N., R. 15 W.) on 30 June 1975 and 8 July 1977. Both observations were of lone birds. These dates provide speculation of possible nesting, although neither nests nor young have been observed.

Habitat: My Douglas County observations were made in a large stand of Lowland Coniferous Forest. Predominant vegetation included trembling aspen, green ash, black spruce, and balsam fir. These vegetative characteristics are usually associated with merlin breeding habitat in their normal breeding range in the boreal forest region of southern Canada. During migration, merlins regularly use a variety of both open and forested habitats.


American Kestrel (Falco sparverius)

Status: Regular migrant, nesting species, and winter resident.

Migration: Abundant migrant in the Western Upland and Central Plain, common in the heavily forested regions of the Northern Highland. Spring migrants arrive in the Western Upland about 5-15 March and the Northern Highland 25 March to 5 April. Peak abundance through the Valley occurs 10-25 April. Fall migration begins in mid-August and peak abundance occurs 1- 15 September. Most fall migrants have departed the Northern Highland by 15 October and elsewhere by 15 November.

Nesting Season Distribution: Common nesting species in the Western Upland and Central Plain, uncommon and more local in the Northern Highland.

Winter: Casual midwinter resident in the Central Plain and Western Upland.

Habitat: Primarily associated with scattered tree groves in agricultural areas, brushy edges of deciduous forest, and Old Field Community in southern areas. In the Northern Highland, American kestrels use edge situations associated with agricultural clearings, and areas that are managed for wildlife production. Wintering American kestrels are usually found along roadsides hunting from transmission wires and occasionally near feeding stations in residential areas.


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