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 peri od 1992-1995. Over the period 1991-1995 gosling growth declined, morta lity during growth increased and local return rate after fledging decr eased. Gosling growth was reflected in final adult body size. Adult ge ese became smaller over the years. This was more pronounced in females than in males. Individual females produced smaller young in later yea rs and also individual adult geese became lighter. All these trends re flect an increasing competition for food over the years. Variation in predation pressure by Arctic Foxes might have amplified the observed t rends by reducing the number of goslings (decreasing gosling survival) and restricting the geese to a small feeding area (decreasing gosling growth rate).