Temperature Dependence of the Breeding Phenology of the Collared Flycatcher Ficedula albicollis in the Białowieża Forest (NE Poland)

Abstract

The breeding phenology of Collared Flycatchers was monitored for 7 years (1993 and 1995–2000) in old- growth, oak-lime-hornbeam stands in the primeval Białowieża Forest. In most years, egg laying commenced in the second half of May. The earliest fi rst-egg date (179 broods) was 1 May, the latest such date was 13 May; these dates diff ered from year to year. The associations between the fi rst-egg date and the mean temperature of the last ten days of April indicated that birds were breeding earlier as a consequence of warmer April temperatures. The earliest hatching date was 21 May, the latest 1 June. Fledging usually started in the fi rst half of June. The length of the breeding season varied from 40 to 53 days and the breeding cycle was negatively related to mean temperature in the fi rst ten days of May