Variation in growth of young and adult size in barnacle geese Branta leucopsis: Evidence for density dependence

A colony of Svalbard Barnacle Geese Branta leucopsis was studied near Ny Alesund, Spitsbergen. Breeding started in 1980 and the colony size followed a sigmoidal curve with little increase in numbers in the period 1992-1995. Over the period 1991-1995 gosling growth declined, mortality during growth increased and local return rate after fledging decreased. Gosling growth was reflected in final adult body size. Adult geese became smaller over the years. This was more pronounced in females than in males. Individual females produced smaller young in later years and also individual adult geese became lighter. All these trends reflect an increasing competition for food over the years. Variation in predation pressure by Arctic Foxes might have amplified the observed trends by reducing the number of goslings (decreasing gosling survival) and restricting the geese to a small feeding area (decreasing gosling growth rate).