Hatching asynchrony, sibling hierarchies and brood reduction in the Chinstrap penguin Pygoscelis antarctica

摘要: We studied patterns of chick growth and mortality in relation to egg size hatching asynchrony during two breeding seasons (1991 1992) a colony chinstrap penguins sited the Vapour Col rookery, Deception Island, South Shetlands. Intraclutch variability was slight not related asymmetry at hatching. Hatching asynchronous 78% (1991) 69% (1992) clutches, ranging from 1 4 days (on average 0.9 1991 1.0 1992). Chicks resulting oneegg clutches grew better than chicks families 1991. In 1992, single same mass 46 age as broods two, suggesting food limitation but 1992. 1991, between siblings flipper length significantly greater synchronous initial guard stage, these differences disappeared later creche phase. body increased with decreased age. Only effect significant for culmen. Asymmetries 15 were similar both years, lower 1992 There relatively frequent reversals hierarchies phases being more common small chicks. survivors brood reduction worse nonreduced broods. attained similarly large sizes before fledging A B rate stage due parental desertions, transition creches (occurs mean 29 days) returned high constant levels when it is mostly starvation (in total 66% hatched survived fledging). contrast, immediately after almost absent older 3 weeks (87% Mortality affected one- two-chick families. suffered probability families, this degree siblings. No association found These results show that there population phase some does facilitate early ensure stable Brood associated prior survival or improve surviving chick. Asynchronous may be consequence thermal constraints on embryo development inducing incubation eggs soon they are laid.