Importance of fat reserves in Wilson´s storm petrel chicks

Abstract

All petrels store large quantities of fat during nesting period. Several hypotheses have offered explanations for the exceptional accumulation of fat by petrels and that stored in smaller amounts by other birds. Fat reserves of Wilson's storm petrel chicks attain 80% of dry mass. Lipid index increases up to value of 2.0 during nesting period . The aim of our study was to explain the role of fat stores in the nestlings. Stable growth of chicks during first three weeks of life suggests that stochastic variation of chick food provisioning arises from unpredictable snow storms rather than fluctuating food availability at the sea. The lack of correlation between body mass and head, tarsal or wing length rejects hypotheses that chicks accumulate lipid in order to increase their rate of intake of a limiting nutrients. Accumulation of excessive lipid reserves may be a consequence of overfeeding of the chicks by their parents. This strategy protects offspring from death during periods of starvation, when nest entrances are covered by snow.