Inter-colony variation in predation, mercury burden and adult survival in a declining seabird.

Migratory species with disjunct and localized breeding distributions, including many colonial marine birds, pose challenges for management and conservation as their dynamics are shaped by both broad oceanographic changes and specific factors affecting individual breeding colonies. We compare six colonies of the declining Leach's storm-petrel, Hydrobates leucorhous, across their core range in Atlantic Canada using standard capture-mark-recapture methods to estimate annual survival of individually marked populations of breeding adults. Over the period analysed (5-20 years per colony; 2003-2022), mean annual survival varied among colonies (0.81-0.88) and annually (process error σ ranging from 0.01 to 0.09), though annual fluctuations were not synchronous across colonies. Two colonies with limited natural predation showed higher survival, and there was a decline in survival with increasing colony-specific total mercury burden. Our work shows that colony-specific pressures and regional contaminant burdens are potentially important contributors to current population declines, and highlights the importance of monitoring demographic rates at multiple sites for species that congregate at key life-history stages.

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Déclaration de conflit d'intérêts

Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Greg Robertson reports financial support and administrative support were provided by Environment and Climate Change Canada. Greg Robertson reports financial support was provided by Environmental Studies Research Fund. The Environmental Studies Research Fund (ESRF: www.esrfunds.org) are monies from Government of Canada levies on the oil and gas industry. The ESRF are directed by a 12-member Management Board which has representation from the federal government (including ECCC), the Canada-Newfoundland and Labrador Offshore Petroleum Board, the Canada-Nova Scotia Offshore Petroleum Board, the oil and gas industry, and the general public. The ESRF is administered by a secretariat within Natural Resources Canada. - GJR on behalf of all ECCC authors.