POPULATION PARAMETERS OF THICK-BILLED MURRES AT COATS ISLAND, NORTHWEST-TERRITORIES, CANADA

About 100 adult and 2,000 nestling Thick-billed Murres were banded at Coats Island annually since 1984. Intensive efforts were made in 1990- 1993 to estimate the reproductive success of birds of known age and to record the band numbers of as many birds as possible. Adult annual su rvival, estimated from the numbers of banded birds resighted, was 87% for females and 89% for males. A capture-recapture estimate for the se xes combined gave a mean annual survival of 89%. The youngest age at f irst breeding was three years, 60% of birds bred at five or younger an d nearly 90% at six or younger. Females started to breed about one yea r earlier than males. Those birds breeding at less than seven years ol d had a lower apparent survival rate than older breeders. Approximatel y 50% of chicks that left the colony were resighted again at three yea rs or older. In each year, the mean success of pairs consisting of two experienced breeders, or of one experienced and one unbanded bird was always higher than that of pairs including young birds of relatively less experience. Reproductive success increased with age to at least n ine years. The survival of breeding murres from Coats Island, and thos e from colonies in Greenland, both of which populations are subject to heavy hunting in their wintering area, is generally lower than surviv al rates of Common Murres populations in Europe and North America, whe re hunting pressure on breeders is lower. The proportion of birds band ed as nestlings that were seen at the colony at three years or older w as high compared to Common Murres in Europe. The high survival rate of young birds is apparently sufficient to offset the additional mortali ty caused by hunting.