- Blackwell, Bradley F.
University of Maine
During 1992-94, I examined temporal and spatial variation in habitat and prey use by double-crested cormorants (Phalacrocorax auritus) over 288 km of the Penobscot River, Maine. In 1993, I also examined foods of nestling double-crested cormorants on 10 island colonies located in Penobscot Bay, Maine, a 35 x 60 km estuarine/marine ecosystem. My objectives relative to the Penobscot River were to examine variation in habitat use, quantify seasonal and spatial variation in cormorant foods during spring, estimate the number of cormorant days-of-predation, and estimate the number of smolts eaten by cormorants. With regard to nestling cormorants my objectives were to compare, temporally and spatially, the diet of nestling cormorants in Penobscot Bay, determine the extent to which Atlantic salmon smolts contribute to the nestling diet, and compare my findings to historic data. To obtain diet information from birds using the Penobscot River, 190 cormorants were collected and stomach contents analyzed. I used aerial and ground surveys to estimate foraging distribution and cormorant numbers. Nestling foods were recovered from 743 regurgitant samples.