Reproductive characteristics and differential response to seasonal temperatures of Blue and Great Tits (Cyanistes caeruleus & parus major) in three neighbouring mediterranean habitats

The breeding ecology of the Blue Tit (Cyanistes caeruleus) and Great Tit (Pants major) was studied for 18 years in three different neighbouring habitats in Sicily, comprising oakwoods, reforested pine and a reforested mix of pine and broad-leaved trees. Both Blue and Great Tits laid eggs up to two weeks earlier in oakwoods than in the reforested areas. Our results indicate a statistically greater breeding success for both species in the oakwoods compared to reforested habitats, with the mixed reforested habitat having a greater success than that of reforested pine habitat. We also correlated reproductive characteristics with local air temperature to verify if the laying date of tits advanced over a long period of years. Even though a variable egg-laying trend was recorded in the three habitats, an overall negative trendline was obtained indicating that the onset of nesting advanced through the 18-year study period. On the other hand, the air temperature trend was positive over the same period of time. The model of covariance analysis showed the relationship between egg-laying and March air temperatures remained consistent for both tit species, it was statistically different for each of the three habitats. Nestlings in the oak habitat fledged one day earlier than in reforested habitats and nestlings in the mixed habitat grew faster than nestlings in the pine habitat. Finally, clutch-size and number of fledglings remained consistent over the 18-year period in all three habitats, suggesting that prey availability may not have changed. Caterpillars comprised the primary prey in the oak and mixed habitats, less in the pine, where tits fed chicks with a more diverse food. The findings of this study indicate the importance of broad-leaved forests, whether natural or regenerated, for insectivorous species, and hence the potential conservation role of forestry management planning.