Relationships among egg size, energy reserves, growth rate, and fasting resistance of Canada Goose goslings from southern Ontario

Abstract

Eggs of wild giant Canada Geese (Branta canadensis maxima) breeding in southern Ontario were collected and incubated artificially. Components of the total nutrient reserve of goslings were measured at hatch to test whether relationships existed between egg size, gosling weight, and weight of reserves in goslings. The growth rate of fed goslings of different weights at hatch was measured for 25 days. The nutrient reserves remaining in goslings of different hatch weights were measured after 2, 4, and 6 days of starvation. Egg size and gosling weight were not highly correlated in this population (r = 0.63). Larger goslings generally contained more reserves than small goslings (P < 0.05), but much variability occurred in this relationship. Gain in weight over 25 days was not related to the weight at hatch. Starved goslings with higher body fat levels had significantly higher dry carcass weights than goslings with low body fat levels (P < 0.01), suggesting a sparing action of fat on body tissues. The apparent survival of small goslings and goslings with small reserves, combined with the great variability in egg size, gosling weight, and extent of metabolic reserves, suggests relaxed selection in the southern Ontario environment where this population breeds.