Apparent Survival of Adult Thayer's and Glaucous Gulls Nesting Sympatrically in the Canadian High Arctic

Abstract

We estimated apparent survival of 33 adult Thayer's Gulls Larus thayeri and 21 adult Glaucous Gulls Larus hyperboreus nesting sympatrically at a small colony on St. Helena Island, Nunavut, in Canada's high Arctic, using five consecutive years (2003–2007) of capture-mark-resight data. Resighting probabilities were high in all years for both species (0.97). Mean survival for Thayer's (0.81 ± 0.05) was low, but for Glaucous Gulls (0.86 ± 0.05) was comparable to estimates of survival reported for large gulls elsewhere. Both species showed high annual variation in survival, with one year each of noticeably lower survival, suggesting that some factors acting on survival may have differed between species and could reflect different species' exposure to natural or anthropogenic stressors. Our findings contribute to the limited demographic information on these polar gulls, and provide a basis for future comparisons should they be affected by changes in their polar environments.