• Johnson, Catherine
  The Graduate School The University of Maine
  

I conducted weekly censuses of islands in Penobscot Bay, Maine and used aerial photographs to determine peak annual nest count dates for Double-crested Cormorants, Herring Gulls and Great Black-backed Gulls. These data also were used to determine the potential effect of survey timing on the ability to detect long-term trends in the abundance of these species. The number of cormorant nests in the study area peaked in mid-June'while Great Black-backed and Herring Gulls peaked in late May and early June'respectively. A 10-year monitoring program using annual surveys conducted between May 23 and June 23 or biennial surveys conducted from June 2 - 17 would have an 80% probability of detecting annual changes of +/- 5% for all three species.