Reliability of Aerial Photography for Detecting Population Trends in Gulls

Abstract

Johnson and Krohn (2001; hereafter,J&K) reported on a series of aerial photographic surveys of breeding colonies of Herring Gulls (Larus argentatus), Great Black-backed Gulls (L. marinus) and Double-crested Cormorants (Phalacrocorax auritus) in Maine. Although their paper was primarily addressed to the timing of surveys, they concluded that "... aerial photos taken during the first few weeks of June can be used to reliably detect population trends in all three species" (p. 31). I believe that this claim was not adequately supported by the information presented either in the paper byJ&K (2001) or in the Ph.D. thesis by Johnson (1998) on which it was based. This information did not