Interannual Variation of Clutch Initiation of the Great Tit (Parus major Linnaeus) in Relation to the Local Air Temperature

The average global climate is changing rapidly¹ and increasing evidence indicates that global warming has consequences on numerous plant and animal species. Previous studies have shown significant fluctuations in the date advancement among wild species phenology in relation to warm springs. For instance, according to Szabó et al.², four out of six investigated plant species in Hungary showed a significant advance in flowering dates by 1.9–4.4 days per decade, and the wood frog (Rana sylvatica) showed a trend toward earlier emergence by 19 days³. In bird species, these impacts often manifest in geographical distribution⁴, population size⁵, interaction between bird species and other species⁶, etc. However, long-term observations were mainly focused on spring migration^7–9 and breeding phenology^10,11 variations. Moreover, while most of the previous long-term monitorings were focused on interannual fluctuations of bird phenology in northern and western Europe, very few were conducted in southeastern Europe.