Gull predation limits nesting success of terns and skimmers on the Virginia barrier islands
O'connell, T.J.; Beck, R.A.
Journal of Field Ornithology 74(1): 66-73
We studied seven mixed-species colonies of terns and skimmers on the Virginia barrier islands in 1990 and 1991 to determine the effect of gull predation on nesting success. We compared intensity of gull predation and other agents of egg or chick mortality between tern and skimmer colonies on islands that also contained nesting gulls and colonies on islands that lacked nesting gulls. Terns and skimmers fledged about 3% of all eggs produced, with confirmed gull predation (27%) and tidal flooding (21%) accounting for the majority of nest failures. Gull-present colonies experienced significantly greater rates of disturbance from Herring and Great Black-backed gulls than did gull-absent colonies. Overall levels of gull predation were similar between gull-present and gull-absent colonies, likely due to the added impact of aerially foraging Laughing Gulls. Anecdotal evidence suggests that nest site competition with Herring and Great Black-backed gulls may have led to many terns and skimmers nesting in areas that were prone to frequent tidal flooding. In addition, floods may have indirectly prevented terns and skimmers from adequately protecting their surviving eggs and young, thus rendering flooded colonies more susceptible to gull predation.