RELATIONSHIP BETWEEN TEMPERATURE AND THE TIMING OF BREEDING OF THE BLUE TIT (PARUS-CAERULEUS) IN 2 MEDITERRANEAN OAKWOODS

Correlations between warmth sum and egg laying in tits (Paridae) were often found but do not prove that there is a direct influence of temperature on egg laying date. Such correlations are also open to criticism because they involve a statistical bias (i.e. the selection of variables). Studies of a Blue Tit population in two close but different habitats in Mediterranean France showed that it is better, at least, to consider a time period with a physiological signification (1 January-10 April). We found that the higher the mean temperature in this time period, the earlier the egg laying commenced. Egg laying dates of the Blue Tit in the two habitats are primarily attributed to habitat-related feeding resources.