YEAR-RELATED AND AGE-RELATED VARIATION IN THE SURVIVAL OF ADULT EUROPEAN SHAGS OVER A 24-YEAR PERIOD

Over 13,000 chicks and 1,800 adult European Shags (Phalacrocorax arist otelis) were banded at a colony in southeast Scotland between 1963 and 1987. Survival estimates for adults (birds three or more years old) w ere calculated from subsequent retrapping of these birds back at the c olony and recoveries of birds found dead in the colony and elsewhere. The mean annual survival for the period 1967-1992 was estimated at 0.8 78 (95% C.I. = 0.859, 0.897). European Shags exhibit considerable annu al variation in several breeding parameters, but there was no evidence that survival was lower in years when breeding was late or reproducti ve output reduced. Survival in years when the number of nests in the c olony showed a dramatic decline was not significantly lower than norma l years. An age-related effect was found indicating that survival decl ined significantly in birds older than 13 years.