ANNUAL AND GEOGRAPHICAL VARIATION IN TIME OF BREEDING OF GREAT TIT PARUS-MAJOR AND PIED FLYCATCHER FICEDULA-HYPOLEUCA IN RELATION TO ENVIRONMENTAL PHENOLOGY AND SPRING TEMPERATURE

Egg-laying by the great tit was closely related to spring temperature. The effective temperature periods became shorter and later with progressive northern latitude and seemed to coincide with a certain phenological stage of the environment. For the pied flycatcher, egg-laying was only weakly correlated with spring temperature and environmental phenology, and nesting took place earlier, in relation to development stage, in late springs and with increasing latitude and altitude of the habitat. The interval between egg-laying in the 2 spp. was shorter in years and areas with delayed spring seasons. This may influence interspecific competition.