Density-dependent foraging and colony growth in a pelagic seabird species under varying environmental conditions

摘要: Intra-specific competition for food resources affects both foraging behaviour and population growth rates in many species, highlighting a need to better understand how changing environmental conditions affect individuals populations of different sizes. Using chick-rearing northern gannets as model, we examined the influence colony size on per capita over 2 time periods (1994-2000 2000-2009) trip durations each years (2000 2009) at 10 colonies separate regions UK Ireland (the North Sea Celtic/Irish Sea). The slope relationship between duration 2009 was less than one quarter that 2000, suggesting much weaker 2009, presumably due intense intra-specific prey sea. There also regional variation, with growing substantially slower their period 2000 did bordering Sea, whilst observed were average 13% shorter predicted from but 32% longer Celtic Irish Seas. These data suggest favourable latter region recent years, annual variation will be particularly marked large colonies, making them especially vulnerable adverse effects low availability