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Numbers and distribution of double-crested cormorants on the upper Mississippi River

Colonial Waterbirds

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Abstract

Historic records indicate that Double-crested Cormorants (Phalacrocorax auritus) were common breeders and abundant during migration on the Upper Mississippi River from St. Paul, Minnesota, to St. Louis, Missouri, during the 1940s and 1950s. Their numbers declined in the mid-to late-1950s, remained low through the 1970s, and began to increase somewhat in the late 1980s. Aerial surveys of migrating cormorants and ground surveys at cormorant colonies during 1991-1993, indicate that numbers have not returned to historic levels. Only 500-2,000 cormorants were seen during spring migration 1992-1993; and 5,000-7,000 during fall migration 1991-1992; whereas, tens of thousands were reported in the 1940s and 1950s. Four hundred ninety-six nests were counted at 4 colonies in 1992, and 545 nests were counted in 9 colonies in 1993; whereas, during the 1940s and 1950s, about 2,500 birds were reported nesting in 4 locations. Pools 6 and 13 have always attracted breeding and migrating cormorants, currently attract the largest numbers of cormorants during migration, and still support breeding colonies.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
Numbers and distribution of double-crested cormorants on the upper Mississippi River
Series title:
Colonial Waterbirds
Volume
20
Issue:
2
Year Published:
1997
Language:
English
Publisher:
U.S. Geological Survey
Contributing office(s):
Upper Midwest Environmental Sciences Center
Description:
pp. 177-184
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Colonial Waterbirds
First page:
177
Last page:
184
Number of Pages:
8