EFFECT OF HATCHING DATE ON BODY AND ORGAN DEVELOPMENT IN GREATER SNOWGOOSE GOSLINGS

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 s upply affected the development of body components of late-hatched and early-hatched goslings in male and female Greater Snow Geese (Chen cae rulescens atlantica). We collected and autopsied 48 early-hatched (EH, mean age at capture = 42.4 days) and 48 late-hatched goslings (LH, me an age = 34.8 days), divided equally among sexes, near fledging at fou r different sites on Bylot Island, Northwest Territories. After statis tically adjusting for differences in body size between the two groups, EH goslings had more body protein than LH ones. However, the developm ent of all organs was not affected equally. The mass of most supplying organs (the food acquisition apparatus: legs, esophagus, intestine, a nd liver), which develop early during growth, was similar between EH a nd LH goslings. In contrast, LH goslings had much smaller breast muscl es than EH goslings, even after adjusting for size differences. Body f at was very low and similar in both groups. Body mass, body protein, i ntestine, 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 compar ed to females. Differences in organ development could reflect an adapt ive response to reduced food availability. Prioritizing the developmen t of supplying organs at the expense of other organs when food availab ility is low could help goslings maintain a high nutrient intake.