• Resource partitioning between breeding common (Uria aalge) and thick-billed murres (Uria lomvia)

      Barger, Christopher Paul; Kitaysky, Alexander; O'Brien, Diane; Takebayashi, Naoki (2013-05)
      In seabirds, food availability is a driver of ecological and evolutionary processes. Here we examine how changes in food availability and energy demands affect both inter-specific resource partitioning and the genetic diversity within a species. We examined the effects of interannual fluctuations in food availability and predictable seasonal increases in energy demands on prey partitioning between breeding common (Uric aalge) and thick-billed (U. lomvia) murres. We observed strong spatial, temporal and dietary differences in the use of prey resources between the species. We found that partitioning increased as food availability declined and as energy demands increased during chick-rearing. We conclude that murres can buffer negative effects of warming and increased energy demands by reducing inter-specific competition for limited food resources. We also investigated the effects of contrasting foraging conditions and population trajectories on the genetic structure of common murres. We found that birds breeding on an increasing food-rich colony had higher genetic diversity than conspecifics breeding on a declining food-poor colony. This may be indicative of changes in a relative strength of purifying selection operating on increasing versus declining colonies. We conclude that foraging conditions might be driving the pattern of the genetic diversity in the Pacific common murre population.