Annual adult survival of Least Auklets (Aves, Alcidae) varies with large-scale climatic conditions of the North Pacific Ocean
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We evaluated whether annual adult survival of Least Auklets (Aethia pusilla), a small planktivorous seabird, covaried with large-scale oceanographic conditions in the North Pacific ocean during 1990–2000. Adult Least Auklets (n=358 total) were captured near their nest sites, marked with plastic color bands, and survival estimates were based on color band resightings at their breeding colony. Survival estimates and relationships between survival and three large-scale indices of climatic conditions that correlate with oceanography: the Pacific Decadal Oscillation Index (PDO), Aleutian Low Pressure Index (ALPI), and North Pacific Index (NPI) were evaluated using program MARK. The best models included: (1) two groups of birds, defined by ease of resighting, that differed in recapture rate (p) but not survival rate (φ); and (2) models that allowed for survival rates to differ in the year immediately after first capture from all subsequent years (structurally an age-model). Both of these model structures effectively explained (i.e. removed) sources of heterogeneity in the data set. For Least Auklet survival, the best fitting model was a two-age model incorporating the covariate NPI (average value for the period auklets were at sea, August – April), [φ(age1, age2×NPI), p(g)]. The annual survival rate varied from 0.747±0.075 SE in 1992–1993 to 0.953±0.052 in 1991–1992 (based on the model [φ(age1, age2×t), p(g)]) and averaged 0.873±0.037 over the study period. Least Auklet annual survival covaried with continuous variation in large-scale climatic conditions. Our results point to oceanographic conditions that relate to climate change as crucial to the status of auklet populations, notwithstanding conservation measures taken to control introduced predators, oil spills, human disturbance and other anthropogenic sources of mortality.
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