Colony size, adult survival rates, productivity and population projections of Black-legged Kittiwakes, Rissa tridactyla, on Fair Isle

The numbers of Kittiwakes on Fair Isle, Shetland, Scotland declined at a rate of approximately 6% per annum between 1987 and 1999. Breeding success over this period was extremely variable but averaged 0.81 young reared per completed nest. Average annual survival of adults between 1986 and 1996 was 86.0% with no significant annual differences. Survival in 1997 (51.6%) was significantly lower and preliminary estimates for 1998 suggested that survival was again low. Using our empirical data for adult survival and breeding success, we estimated a 20% survival from fledging to recruitment and an age of first breeding of 4-5 years. Incorporating these values into a simple population model indicated that the Fair Isle colony will decline by a further 13-48% over the next three seasons.