MEPS 565:217-226 (2017)  -  DOI: https://doi.org/10.3354/meps11999

ABSTRACT: Prey availability around seabird breeding colonies is often unpredictable, with prey fluctuating in both abundance and distribution. This study examined the effects of natural and experimentally altered food intake on growth and physiological condition in Atlantic puffin Fratercula arctica chicks during 3 breeding seasons. Previous studies have shown that food-supplemented chicks generally do not gain more mass than control chicks, because parents of food-supplemented chicks reduce their provisioning effort in response to the decreased food requirements of their offspring. In contrast, food-supplemented chicks in this study gained significantly more mass per day and had greater tarsus and wing growth than control chicks. Consistent with available information on capelin spawning, our results suggest that prey availability was generally so poor that parents could not reduce provisioning effort, even when extra food was provided. Corticosterone was significantly higher in control chicks compared with food-supplemented chicks, which is consistent with some, but not all, previous studies. Chicks had lower mass when prey availability was poor, but this was associated with high corticosterone levels only when weather conditions were also poor. These results suggest that measuring multiple fitness indices can be useful for determining overall environmental conditions and can provide insight into how puffins are adjusting to changes within their ecosystem.

KEY WORDS: Atlantic puffins · Chick growth · Corticosterone · Foraging conditions · Supplemental feeding