Egg dimensions of the great Tit [Parus major L.] in Croatia

This study took place in the rural area (Hrvatsko Zagorje), in north-western Croatia.The study period lasted from March to April 1999. Only the first clutch was analysed. On an area (614 ha) of deciduos wood 90 nest-boxes were used. There was no statistically significant correlation between clutch size and the dimensions of eggs, as well as between egg dimensions and reproductive variables. There is nosignificant correlation between female body weight and clutch size as well. So we can conclude that the results of our research do not support predictions based on the theory of optimal clutch/egg size.