Effect of hatching date on body and organ development in Greater Snow Goose goslings

Abstract

Growth rate in geese is sensitive to the feeding conditions during the brood-rearing period, and late-hatched goslings grow at a lower rate than early-hatched ones. We examine how the seasonal decline in food supply affected the development of body components of late-hatched and early-hatched goslings in male and female Greater Snow Geese (Chen caerulescens atlantica). We collected and autopsied 48 early-hatched (EH, mean age at capture = 42.4 days) and 48 late-hatched goslings (LH, mean age = 34.8 days), divided equally among sexes, near fledgling at four different sites on Bylot Island, Northwest Territories. After statistically adjusting for differences in body size between the two groups, EH goslings had more body protein than LH ones. However, the development of all organs was not affected equally. The mass of most supplying organs (the food acquisition apparatus: legs, esophagus, intestine, and liver), which develop early during growth, was similar between EH and LH goslings. In contrast, LH goslings had much smaller breast muscles than EH goslings, even after adjusting for size differences. Body fat was very low and similar in both groups. Body mass, body protein, intestine, and breast muscles showed a sexual dimorphism favoring males in EH, but not in LH, goslings. These results show that poor feeding conditions encountered by LH goslings disproportionately affected late-developing organs compared to early-developing ones, and males compared to females. Differences in organ development could reflect an adaptive response to reduced food availability. Prioritizing the development of supplying organs at the expense of other organs when food availability is low could help goslings maintain a high nutrient intake.