Fatty acid signatures of female Brconnich's guillemots Uria lomvia suggests reliance on local prey for replacement egg production

摘要

The laying of smaller replacement eggs has been described as a time-saving adaptation because chicks generally grow faster once hatched than inside the egg. However, chicks hatched from smaller eggs have, potentially, lower survival. Consequently, the smaller replacement egg represents a benefit to the female in terms of preserving its own condition at a cost to their offspring. We test these ideas by measuring adult mass changes and plasma lipid concentration changes in male and female Brconnich's guillemots Uria lomvia breeding on Coats Island, Nunavut. Though males lost more mass than females, these differences were not significant. Between laying the first and replacement egg, plasma fatty acid concentrations declined in females and increased in males, suggesting that females mobilise less lipid to preserve their condition after laying the replacement egg. In females, plasma lipid concentrations of the dominant fatty acids found in the eggs (16:0 and 18:1) declined between the laying of first and replacement eggs while plasma concentrations of 20:1 increased in both males and females. We compared the fatty acid signatures of first and replacement egg to look for evidence of differences between the lipid sources for their production. Principal component and discriminant function analyses showed that the fatty acid signatures of replacement eggs were closer to the signatures of the local prey than those of first eggs. We suggest that females rely on local sources of energy to a greater degree for the production of the replacement egg than the first egg, but that endogenous reserves of certain nutrients are important for the production of both eggs.