Variation in Egg Composition in Semi-Captive Barnacle Geese

Abstract

Egg composition was examined in a semi-captive flock of Barnacle Geese Branta leucopsis in relation to egg size, laying sequence and to the age, size and aggressiveness of the male and female. The proportion of yolk in the eggs was within the normal range for precocial species, but the proportion of lipid (14%) was high even in comparison with other geese. The last egg was the smallest of the clutch, but the proportions of yolk and lipid were independent of egg size and laying sequence. Egg composition did not vary with the date of clutch initiation. There were no significant correlations between body weight and size, aggressiveness or breeding experience of either male or female and egg composition. Although there were no significant differences in weight and dimensions of egg from different sized clutches, there was a significant negative correlation between clutch size and the amount of yolk and of lipid. Eggs in repeat clutches were similar in size to those of the first clutch, but had lower proportions of both yolk and lipid. This indicated some compromising of the energetic commitment to individual eggs in relation to an environmental factor (in captivity need for re-laying to be rapid if it is to be successful, or change in food quality).