Survival of the kittiwake in relation to sex, year, breeding experience and position in the colony.

Abstract

1. Continuous monitoring of a colony of marked kittiwakes has led to 34 years of data on the survival of individual birds, as well as on breeding success, mate fidelity and site tenacity.
2. Generalized linear modelling showed that the annual adult survival rate of the kittiwake varied according to sex, time-period, breeding experience and nest position. The effect of each factor was apparently independent of those of the other three.
3. The average annual survival rate of adult males was 78% and that of females 82%, after allowing for the effects of factors other than sex. Throughout the study, the survival odds for males were 0.8 times those for females.
4. First-time breeders survived as well as experienced birds which had been breeding for up to 12 years; beyond 12 years, the annual survival rate dropped by 11% on average.
5. Long-term changes in the annual adult survival rate of the kittiwake were not an artefact of the changing age structure of the colony through time. After removing the effect of age, the annual survival rate was highest during 1958- 61, lowest during 1982-85; between these two periods, the mortality rate tripled.
6. Kittiwakes which settled in either the centre or the edge of the colony did so for life. Males and females that nested in the centre survived better than ones on the edge throughout the study (average of 81.2% versus 78.7% year^-I). The difference probably reflected a segregation between intrinsically fit and less fit individuals: the two areas were equally safe to nest in, but centre birds had a higher breeding success and lifetime reproductive fitness than edge birds.