Repeatability of Clutch Size in Female Starlings (sturnus Vulgaris)

Theories of clutch size determination have focused on first broods or on seasonal trends in clutch size. Clutch size is controlled by combination of genetic, ontological and environmental factors (KENNEDY & WHITE, 1991). In recent years, an increasing number of studies have demonstrated the existence of significant repeatability in ecologically important traits in natural bird populations (e.g. GOODBURN, 1991; JERZAK et al., 2000; AMAT et al., 2001; YOSEF & ZDUNIAK, 2004). Repeatability expresses the proportion of the variation between measurements that is due to consistent differences between the objects measured (HÕRAK et al., 1995). According to van NOORDWIJK et al. (1980), no single optimum value exists for clutch size. In some years small clutches are optimal, in other years large clutches contribute more to NAT. CROAT. VOL. 14 No 4 357¿361 ZAGREB December 31, 2005