Prerequisites for recruitment of Kittiwakes Rissa tridactyla

Observations at the North Shields Kittiwake colony between 1982 and 1984 showed over 100 potential recruits (birds of breeding age) associated with the colony, only about 40% of which were actually recruited. In addition, there were younger birds which visited the colony. The origins, age structure and intercolony movements of members of the pool of prospectors have been examined. Porter & Coulson (1987) demonstrated that recruits are heavier than prospectors, implying that they are in better body condition. Three further prerequisites for breeding in Kittiwakes are recognized: the age of recruits is at least three years; all birds which recruit are present at the colony at least one year prior to breeding; and recruits show a high degree of attachment to colony as illustrated by their colony and nest site tenacity, attendance and early arrival. The results suggest that there is considerable selection of individuals at the time of recruitment; the mechanism for this has yet to be examined.