The population dynamics of Northern Fulmars (Fulmarus glacialis) were studied at the Semidi Islands in the western Gulf of Alaska. Fulmars occurred in a broad range of color phases, and annual survival was estimated from the return of birds in the rarer plumage classes. A raw estimate of mean annual survival over a 5-year period was 0.963, but a removal experiment indicated the raw value was probably biased downward. The estimate of annual survival adjusted accordingly was 0.969. Mortality during the breeding season was less than 10% of the annual total, and postbreeding mortality of failed breeders was three to four times higher than that of successful breeders. Breeding success averaged 41% over 9 years. About 5% of experienced birds failed to breed each year due to physical destruction of their breeding sites, mate-loss, or other causes. An estimated 30% of the birds near the colony in one year were of prebreeding age. A comparison of population parameters in Pacific and Atlantic fulmars indicates that higher survival in the prebreeding years is the likely basis for population growth in the northeastern Atlantic. The correlation of breeding success and survival suggests both parameters may decline with age.
