FOURNIER, Francois; GAUTHIER, Gilles; Universite de Moncton; Universite Laval: The effect of food quality on developmental plasticity and digestive efficiency in greater snow goose goslings

Geese, one of the few herbivorous groups of birds, face a series of unique constraints during growth. (1) Goslings must feed by themselves (precocial); (2) they must attain a large size during a short growing season; (3) most of them grow in the Arctic under harsh climatic conditions; and (4) young feed exclusively on plants. The consequence of these constraints is that growth rate is highly sensitive to environmental conditions encountered early in life. We examined how the quality of food (high vs low) have shaped the growth strategy in this group of birds, using the greater snow goose as a model. Birds in all experimental groups gained body mass, although birds in the low-quality diet group gained mass more slowly than those in the high-quality group. Digestive efficiency differed among groups with gosling in the low-quality diet group having the lowest efficiency. Individuals consuming the low-quality diet had a higher intake of dry matter than those on the high-quality diet, and this higher rate of intake did not decrease with age in the low-quality group. There was no difference in morphological growth, but internal morphology differed. Gosling feeding on the lower-quality diet had heavier gastrointestinal tracts whereas birds consuming the higher-quality diet had heavier pectoral muscles. If food abundance and/or quality are reduced, goslings have little ability to compensate, and because goslings must fledge in time for the fall migration before the fall freeze up, those that hatch late and/or grow more slowly must fledge at a smaller size and will retain this small body size for the rest of their life.