Predation risk and settlement decisions by colonially nesting Black Brant (Branta bernicla nigricans)

Colonial nesting is associated with numerous costs and benefits that may either increase or decrease fitness of individuals in colonies. Fitness can vary as a function of the location within colonies and individuals may attempt to improve their fitness by changing their nesting location between years. We used a 24 year data set on nest locations within the Tutakoke River Black Brant (Branta bernicla nigricans) colony on the Yukon-Kuskokwim Delta in western Alaska and multi-state capture-mark-recapture models to study the movement of individuals between 2 spatial strata in the colony separated by the Tutakoke River. We found that individuals nesting in a stratum that experienced higher levels of predation by arctic foxes (Vulpes lagopus) were 3 times more likely to move to the other stratum than vice versa, despite slightly higher risk of tidal flooding in the second stratum. These results suggest that Black Brant changed nest locations in an attempt to maximize reproductive fitness and they are consistent with a long-term shift in nest density over the course of the study.