The case for lethal control of gulls on seabird colonies

Published source details Scopel L.C. & Diamond A.W. (2017) The case for lethal control of gulls on seabird colonies. Journal of Wildlife Management, 81, 572-580.
Share Tweet Email

Summary

A 2017 review of tern Sterna spp. colonies in eastern North America (Scopel & Diamond 2017) found that controlling gulls Larus spp. and Leucophaeus sp. typically had no significant effect on tern productivity or predation rates. Clutch size did not significantly differ between colonies with and without gull control in 8 of 11 comparisons (for which lethal control: 1.7–2.3; non-lethal control: 1.7–2.1; no control: 1.7–2.4). In the other three comparisons (including two of four comparisons involving non-lethal control), clutch size was smaller in colonies with gull control than without. Fledgling production did not clearly or significantly differ between colonies with and without gull control in 8 of 11 comparisons (for which lethal control: 0.5–1.1; non-lethal control: 0.8; no control: 0.4–1.1 fledglings/nest). Results in the other three comparisons were mixed. Predation rates were lower in colonies with lethal gull control (10–12% of eggs and chicks depredated) than without gull control (38%) in two of two comparisons, but did not significantly differ between colonies with non-lethal gull control (28%) and no control (38%). For comparisons of the effects of lethal vs non-lethal control, see original paper. This review used data from 23 published studies carried out in eastern North America (344 data points) plus unpublished data from the Gulf of Maine (993 data points). It focused on four tern species. Data were collected between 1967 and 2014. The authors extracted one data point for each combination of metric x species x colony x year. Data points were classified by the most aggressive form of gull control carried out: lethal control by shooting or poisoning; non-lethal control by egg or nest destruction, deterrence or scaring; no control (but gulls present).