We followed the reproductive parameters of two species of tits, Great and Blue tits, over three decades (1993–2022), in three close habitats of the Mediterranean island of Sicily. We found that they regulated egg-laying dates in the same way, even though they had different dates. The anticipation of laying dates was inversely correlated with the temperature trends of February. The Great tit showed a significant anticipation of laying dates in all three habitats: in the pine woodland, an average anticipation of 19.8 days in 30 years was observed; in the oak woodland, an anticipation of 10.5 days in 30 years was seen; and in the mixed woodland, an anticipation of 13 days in 26 years was seen. The tendency to anticipate the laying date was also observed for the Blue tit in all habitats: in the pine woodland, it significantly anticipated the laying date by 14.4 days in 30 years, while in the oakwood, the anticipation was slightly smaller at 8.7 days in 30 years, and in the mixed woodland, an anticipation of 13.8 days in 26 years was observed. Breeding success did not change over the years for both species. Although we observed through the recoveries of ringed tits a movement of breeding individuals from the pine to the oakwood, we never observed the opposite. This is likely due to the greater availability of feeding resources in the natural woodland. In fact, tits in oak forests feed mainly on caterpillars; in other woodland types, they do not find caterpillars and feed on other arthropods. We hypothesize that most likely in Sicily, these tits, thanks to their phenotypic plasticity, will adapt to the present new conditions resulting from global warming, but if temperatures rise further, they will certainly face difficult times.
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