Composition of Blue-Winged Teal Eggs in Relation to Egg Size, Clutch Size, and the Timing of Laying

Abstract

Blue-winged Teal (Anas discors) eggs from 172 nests were analyzed to determine how organic composition was affected by clutch size, laying sequence, nest attempt, laying date, and egg size. On average, eggs weighed 28.1 g and were 46% yolk and 44% albumen. Eggs contained 3.6 g lipid and 3.2 g protein almost equally distributed between yolk and albumen. Yolk increased a disproportionate amount and the proportion of albumen tended to decrease with increased egg mass. Consequently, large eggs contained proportionately more lipid than small eggs. Shell decreased in proportion with increasing egg mass. For most egg traits 60 to 80% of the variation occurred between clutches rather than within clutches. Teal eggs did not vary in composition in relation to clutch size, laying sequence, nest attempt, or the timing of laying on either a seasonal or yearly basis. Eggs in renests weighed 0.8 g less than eggs from the first clutch of the same females; however, this disparity was not reflected in differences in lipid or lean dry mass for the collected eggs of known renesters.