Clutch size of the Great Tit Parus major and the Blue Tit Parus caeruleus in some areas of Centrai Italy
BELLAVITA M. and SORACE A.Abstract:
Small values of clutch size were observed for both species in ali the study stations, as compared with other European areas located at higher latitude; these results could be related to the lower seasonality of food resources in Mediterranean area. In some sites preliminary data show a high presence of youngsters among the breeders; considering also the small effect of competitive factors and predation on clutch size, a trade-off between reproduction and survival does not appear to be important. As far as cJutch size variations among the study areas are concerned, habitat features, density of breeders and laying date seem to play a decisive role. Clutch size does not decrease with altitude. Food availability might produce the observed differences in breeder density.