Northern Prairie Wildlife Research Center
Status: Regular migrant and nesting species.
Migration: Common (locally abundant) during spring and fall throughout the Valley. Spring migrants arrive in the Western Upland during the first week of April (earliest-4 April 1964, St. Croix County; Soulen 1965) and the Northern Highland 10-15 April. Peak spring abundance occurs 20 April to 1 May. During this period flocks of 5 to 10 birds are common and flocks totaling 15 to 20 are occasional on larger lakes. Spring departure from the southern one-third of the Valley occurs by 15 May. Fall migrants arrive in the Western Upland during the first week of October and remain until water on the larger lakes freezes in late November. No major common loon staging areas exist in this region, resulting in relatively small numbers observed during the fall.
Nesting Season Distribution: Uncommon nesting bird on larger lakes and marshes of the Northern Highland, rare and local in the Central Plain. Casual summering birds near Roberts, St. Croix County, indicate possible nesting although no broods have been observed. Longley (1949) reported a pair with one young in Washington County on 17 June 1949. Additional Washington County brood records were obtained in 1970 and 1971 (Eckert 1971).
Habitat: Common loons are primarily a species of large permanently flooded wetlands, particularly those containing small islands. Most wetlands used for nesting are bordered by deciduous forest, chiefly trembling aspen and maple, and contain peripheral zones of emergent aquatic vegetation. At the Crex Meadows Wildlife Area in Burnett County, common loons nest on semipermanently and permanently flooded wetlands. The vegetation consists primarily of cattail and various species of sedge. Evrard et al. (1978) found that common loons at Crex Meadows occupied wetlands that ranged from 6.9 to 324 ha.
Concern has been expressed recently about the population status of this species in Wisconsin, Minnesota, and other northern States. The primary threat to the nesting habitat of this species is shoreline development surrounding nesting lakes.
Status: Casual migrant; one summer record.
Records: Spring records include Pierce County-10 May 1967; St. Croix County-25 April 1962 and 17 May 1965; Burnett County-15 May 1950 (Robbins 1950b). During the summer of 1953 a nonbreeding red-throated loon was observed on 11 June and 17 July at Crex Meadows Wildlife Area, Burnett County.