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ARS Home » Southeast Area » Stuttgart, Arkansas » Harry K. Dupree Stuttgart National Aquaculture Research Cntr » Research » Publications at this Location » Publication #168044
Title: INADEQUACIES OF OVER-WINTERING POPULATION ESTIMATES OF DOUBLE-CRESTED CORMORANTS AND CONSPECIFICS FROM AQUACULTURE PRODUCTION SITES AND SURROUNDING AREAS

Author
item Radomski, Andrew

Submitted to: American Ornithologists' Union Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/18/2004
Publication Date: 8/16/2004
Citation: Radomski, A.A. 2004. Inadequacies of over-wintering population estimates of double-crested cormorants and conspecifics from aquaculture production sites and surrounding areas [abstract]. American Ornithologists' Union Annual Meeting. p. 165.

Interpretive Summary:

Technical Abstract: Now that the U.S. Fish and Wildlife Service and the Canadian Wildlife Service have national Double-crested Cormorant (Phalacrocorax auritus) plans, it is imperative to understand the spatial and temporal population trends. Given that there has been a paucity of rigorous long-term studies on the over wintering numbers of cormorants in the commercial aquaculture producing areas of the southeastern U.S., understanding these changes will be important to the management strategies at aquaculture facilities. Therefore, within Arkansas (USA), aerial surveys by fixed-wing aircraft will continue to be used to fulfill these needs of monitoring and quantifying the wintering cormorant numbers. Since 1999, cormorant estimates were conducted during the last 3 hours of sunlight and encompassed catfish production areas in Arkansas. A minimum of 2 surveys per month was conducted along a fixed route. Survey flights were usually conducted on consecutive days. Aerial counts were validated with ground observations the following morning at specific roosts for accuracy. A minimum of 16,000 cormorants was observed during each survey, with the exception of early January 2000 and 2001. Cormorant numbers peaked (>26,000) in early February 2001 and a total of 12 to 15 night roost sites were monitored during 1999-2004. Cormorants roosted in bald cypress trees almost exclusively. Some roosts were protected from human disturbances, but some were adjacent to highways or adjacent to high recreational areas. Similarities in numbers of cormorants counted in the evening by aircraft and the following morning by ground observers at the same roost allows for increased confidence that the estimates are reasonably accurate.