REPRODUCTIVE SUCCESS OF THE KITTIWAKE RISSA-TRIDACTYLA - THE ROLES OF CLUTCH SIZE, CHICK GROWTH-RATES AND PARENTAL QUALITY

Kittiwake growth rates and breeding success are examined in relation to survival between fledging and breeding and to adult survival rates. High chick growth rates lead to increased survival after fledging. Broods of three (the maximum brood size) did not suffer lower fledging success than broods of two and clutches of three fledged appreciably more chicks per pair than did clutches of two or one. On average, the a- and b-chicks in broods of three grew at a faster rate and had a higher survival before breeding than those from smaller broods. Chicks from broods of two with experienced female parents grew at a faster rate than those of inexperienced female parents. Female parents which laid three egg clutches had a higher survival rate than those which laid clutches of two or one. We contend that three egg clutches were laid by higher quality individuals. We believe that clutch size indicates the condition of the Kittiwakes forming the pair. This condition probably has a genetical component, but is modified by environmental factors.