Development of an arctic barnacle goose colony:Interactions between density and predation

The development of a barnacle goose Branta leucopsis colony established in 1980 was studied from 1989 to 1997 using sightings of marked individuals. The number of adult geese was calculated using a Petersen estimate. Alternatively, the number of adult geese was based on estimates of gosling production and local return late based on Jolly-Seber models. Both methods showed similar results and were close to censuses in 1996 and 1997. The local population increased rapidly up to 1993. Thereafter the growth rate levelled off, due to a decrease in both local return rate and gosling production. The local return rate was lower for goslings than for adults and females were more philopatric than males. The production of goslings was related to the presence of arctic foxes Alopex lagopus in the area. in the period 1992-95, predation by arctic foxes lowered the number of fledged goslings and moreover resulted in local crowding which had a negative effect on the growth rate of goslings and adult body condition. This density dependence was related to the presence of arctic foxes. Comparing years without foxes, before 1992 and after 1995, the population showed a three-fold increase but there was no difference in gosling production or gosling growth.