Morphometric and allometric studies on eggshells and embryos of free-living Canada geese (<Emphasis Type="Italic">Branta c. canadensis</Emphasis> Linnaeus, 1758)

A total of 289 eggs laid by free-living Canada geese (Branta canadensis canadensis Linnaeus, 1758) in the northwestern part of Germany were collected in spring 2002 and 2003 and examined for shell and embryo parameters. Mean egg mass was 160.88±19.68 g. Approximately 90% of all eggs had a mass between 140 and 185 g. About 90% of all clutches consisted of four to seven eggs. The form index of 90% of all eggs was in the range 62–74. The mean eggshell thickness on the blunt pole was 0.52±0.08 and 0.53±0.07 mm on the long axis. Embryo development follows a square function in the first half of development. Mean embryo length was correlated (P<0.01) with the mean body mass and shell thickness on the blunt pole and on the long axis of the eggs. No significant correlations were found between egg mass and form index and egg mass and shell thickness. Eggs with no visible fertilisation had a mean form index of 68.69±4.53 and fertile eggs had a mean form index of 68.50±3.73. Only 3 of 160 fertile eggs contained embryos with malformations of the beak, vertebral column, or leg. The question of regulating prevailing Canada goose populations is discussed.