Egg dimensions of the Great Tit Parus major in southern Finland

Abstract

Factors affecting the egg dimensions of the Great Tit in southern Finland (60° 15'N) were studied in 1975-1977, using the mean clutch values of 99 first clutches. The mean egg length was 17.86 mm (SD = 0.59) and the mean eggbreadth 13 .45 mm (0.31) . There were no annual, seasonal, clutch size-related or female age-related differences in egg dimensions. Female body weight and warm weather during the egg-laying period had positive effects on egg size . Egg size seemed to be greaterin northern Lapland (69°N) than further south in Norway and Finland. The correlation between egg length and egg breadth was the same in four different study areas, but heterogeneity was evident in the relationship between egg size and clutch size.