BREEDING ECOLOGY OF THE BLUE TIT PARUS-CAERULEUS IN EASTERN SPAIN - A COMPARISON WITH OTHER LOCALITIES WITH SPECIAL REFERENCE TO CORSICA

Aspects of the breeding ecology of the Blue Tit Parus caeruleus were studied in intermediate stages of succession in a holm oak forest at Monte Poblet (eastern Spain) from 1985 to 1991. In different years the density in two plots without nest-boxes varied between 1.0 and 6.5 pairs per 10 ha. Nestbox introduction seems to have increased the density of breeding pairs. The mean laying date was earlier (6 vs. 13 May) in low altitude (500-750 m a.s.l.) plots than in a high altitude (900-1000) m a.s.l.) plot, but clutch size (6.9 vs. 6.5 eggs) was not significantly different (mean 6.6 eggs). No differences in mean laying dates were found between years. Significant differences in clutch size were found only between two years at the high altitude site. There was a slight, non-significant, seasonal decline in clutch size. No second clutches were laid. These results are discussed in the context of other Mediterranean studies with special focus on the differences and similarities between Corsican and mainland populations. It is shown that most of the characteristics of the Corsican population (i.e. density, habitat use, laying date, clutch size, number of broods per year) are shared by some populations on the mainland. On the other hand, some breeding traits of Blue Tit populations in southern France are closer to those of Central and North European populations than to the Iberian ones.