S38-4 The effect of environmental conditions on early growth in geese

Geese, one of the few avian herbivores, face a combination of unique constraints during growth. Goslings must feed by themselves; they must reach a large size during a short growing season; they grow in the Arctic under harsh climatic conditions; and, despite their high nitrogen requirement for growth, they feed only on plants, which are low in protein. We examined how these constraints shape growth strategy in the greater snow goose (Anser caerulescens atlanticus). Growth rates of goslings are among the highest reported in precocial birds. Goslings maintain a very high resting metabolic rate throughout growth and are fully competent homeotherms soon after hatching: they seem to prioritize maintenance of optimum internal conditions for biosynthetic activity over energy conserving strategies. Such an expensive life-style can only be sustained by feeding at a very high rate on high-quality food. The consequence is that growth rate is highly sensitive to environmental conditions encountered in early life. Although the developmental pattern in goslings shows some phenotypic plasticity when environmental conditions deteriorate, it is not sufficient to compensate for factors such as a seasonal decline in plant quality. Therefore, goslings that hatch late or grow slowly must fledge at a smaller size, and this may have serious fitness consequences for survival and adulthood.