Skip to main content
U.S. flag

An official website of the United States government

The importance of survey timing in monitoring breeding seabird numbers

January 1, 2001

We conducted weekly aerial surveys of islands along the central Maine coast from April-June of 1993-1997 and used aerial photographs to determine peak nest count dates for Double-crested Cormorants (Phalacrocorax auritus), Herring Gulls (Larus argentatus) and Great Black-Backed Gulls (Larus marinus). 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. Peak nesting dates generally were consistent for each island across years, but varied by up to a month between islands during a given year. A 10-year monitoring program using annual surveys conducted between 23 May and 23 June, or biennial surveys conducted from 2-17 June, would have an 80% probability of detecting annual changes of ??5% for all three species in this region. Received 1 November 2000, accepted 4 December 2000.

Publication Year 2001
Title The importance of survey timing in monitoring breeding seabird numbers
Authors C.M. Johnson, W.B. Krohn
Publication Type Article
Publication Subtype Journal Article
Series Title Waterbirds
Index ID 70023651
Record Source USGS Publications Warehouse