EFFECTS OF HATCH DATE AND FOOD-SUPPLY ON GOSLING GROWTH IN ARCTIC-NESTING GREATER SNOW GEESE

We studied the effects of hatch date and food supply on growth of goslings of the Greater Snow Goose (Chen caerulescens atlantica) at Bylot Island, Northwest Territories, Canada. Two groups of goslings were collected and imprinted on humans, one early (n = 15) and one late (n = 19) in the hatching period (span of 5-7 days). Early and late-hatched groups were each divided into food supplement and control treatments. Goslings from control groups fed exclusively on natural vegetation throughout the summer whereas those from the food-supplemented groups had access to a high-protein commercial diet for 12 hr each day. Early-hatched goslings grew faster, and were heavier and larger at 40 days (near hedging) than late-hatched goslings. Food-supplemented goslings also grew faster, and were heavier and larger at 40 days than controls. Plumage (9th primary) developed at a younger age when goslings hatched early or received a food supplement but plumage growth rate was constant among groups. Early-hatched goslings survived better than those hatched late, irrespective of feeding treatment. More late-hatched, food-supplemented goslings survived than late-hatched controls, but the difference was not significant. Goslings that were lighter than the mean were more likely to die than heavier ones at any given age. We conclude that differences in growth and possibly survival between early and late-hatched goslings are food-mediated and largely caused by the rapid decline in quality of arctic plants during the summer. Differences as small as 5-7 days in hatch dates may have major fitness consequences in arctic-nesting geese.