Effects of cohort and individual variation in duckling body condition on survival and recruitment in the Common Eider Somateria mollissima

The relationship between juvenile body condition and pre-reproductive survival and recruitment of female Common Elders was analysed in three duckling cohorts marked in the Stavns Fjord colony, Denmark during 1991-1993, based on recoveries of females in the colony in 1996. Mean duckling condition differed significantly between the three cohorts, but recruitment was not affected by this difference, c. 18% having recruited from each cohort in the third year after ringing. Compared to mean cohort condition, in all years a positive relationship existed between individual duckling condition and recruitment, irrespective of duckling size at capture. The present results suggest that survival and recruitment of female elders were related to the relative body condition attained as ducklings within cohorts rather than related to the absolute condition attained by separate cohorts.