Comments on recent canvasback habitat trends and threats on Chesapeake Bay

Hosted by North Dakota Game and Fish Department and the Northern Prairie Wildlife Research Center, U.S. Fish and Wildlife Service. Sponsors, Central Mountains and Plains Section and North Dakota Chapter of the Wildlife Society.


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During the last 22 years, the North American winter population of canvasbacks has fluctuated from 481,000 in 1955 to 179,000 in 1972. The Chesapeake Bay population has averaged 33 percent of the North American population and 64 percent of the Atlantic Flyway population. In Maryland, significant annual fluctuations have been recorded between the eastern and western shore of Chesapeake Bay. In 1968, 11 percent of the Bay canvasbacks were on the western shore, whereas in 1971, 87 percent of the birds wintered in this area. This increase in 1971 is believed to be in response to large populations of small Rangia cuneata clams. I n recent years, mortality of small clams and reduced spawning have resulted in a larger size class for Rangia making them less desirable as a waterfowl food. Canvasback populations in 1975 and 1976 were more dispersed in Chesapeake Bay when the predominant food of canvasbacks was Macoma balthica. In the last 5 years, the number of canvasbacks wintering in Chesapeake Bay has declined slightly, while the North American and Atlantic Flyway populations have increased. Increases have been noted in New Jersey and North Carolina. This trend may indicate that the quality of canvasback habitat in Chesapeake Bay is declining at a faster rate than other areas along the Atlantic coast.

Additional publication details

Publication type Book chapter
Publication Subtype Book Chapter
Title Comments on recent canvasback habitat trends and threats on Chesapeake Bay
Year Published 1976
Language English
Publisher North Dakota Game and Fish Department
Publisher location Bismark
Contributing office(s) Patuxent Wildlife Research Center
Description v, 63
Larger Work Type Book
Larger Work Subtype Other Government Series
Larger Work Title Transactions of the Canvasback Workshop : April 6-7, 1976, Ramada Inn, Jamestown, North Dakota
First page 17 (abs)