Northern Prairie Wildlife Research Center
Status: Regular migrant and nesting species. The Wisconsin Department of Natural Resources (WDNR) has listed this species as endangered (Les 1979). Loss of nest trees, use of pesticides, and human disturbance are listed as reasons for their decline.
Migration: Rare and local migrant throughout the Valley. Formerly a common to abundant migrant throughout its range, populations of double-crested cormorants have experienced alarming declines. Records exist of "flocks of thousands" migrating north along the Mississippi and St. Croix rivers until the 1950's. Currently, observers are fortunate to find more than 25 individuals during the year. The average date of spring arrival is 18 April (earliest-4 April 1976, Chisago County). Peak spring migration occurs 25 April to 10 May, and departure from nonbreeding areas by 25 May. Peak fall migration occurs between 10-20 September and departure by 15 October (latest-3 November 1975, Burnett County).
Nesting Season Distribution: Double-crested cormorants are rare and local during the nesting season in this region, currently known to nest only at the Crex Meadows and Fish Lake Wildlife Areas in Burnett County. The first nesting was noted at Crex Meadows in 1968. This colony was in a heron rookery on Phantom Lake. Because of degradation of nesting trees, the Phantom Lake colony declined, and birds moved to the Grettum Flowage at Fish Lake Wildlife Area. In 1973, 23 nests were observed in the Grettum Flowage colony.
Habitat: Both Phantom Lake and Grettum Flowage are large impoundments characterized by deep water and dead trees. This temporary habitat type was created when tree growth in these basins was inundated by rising impounded waters. Construction of nest platforms in the Phantom Lake colony has attracted several breeding pairs. This management practice may prove essential in the maintenance of these two colonies.