Variation and long-term trends in the timing of breeding of different Eurasian populations of Common Redstart Phoenicurus phoenicurus

Abstract

Changes in the timing of reproduction of birds should provide good evidence of large-scale climate fluctuations. However, geographically separate populations of one species may respond variably. We analyzed egg laying dates of nine Eurasian populations of the Common Redstart Phoenicurus phoenicurus collected between 1969 and 2010. The timing of breeding differed greatly with latitude: the populations in the north started later, a breeding pair produced only one brood per season and the breeding season was shorter. Both yearly minimum and median first-egg laying dates advanced with increases in local air temperature, but the more northern populations had started at much lower temperatures, which was probably caused by the stimulation of photoperiod. The effects of large-scale climatic patterns (North Atlantic Oscillation, East Atlantic, Scandinavia/Eurasia-1) on the first-egg laying date were low. The egg laying dates advanced over the observed decades in all populations, although at a variable rate. Seven selected populations with the most complete data for the period 1986–2010 revealed an advancement of median first-egg laying dates of 0.11 days/year and 1.31 days/°C. The effect on minimum first-egg laying dates was smaller. The changes observed in two populations in Ural and western Siberia were smaller than those found in more westerly populations (Finland, central Europe). The timing of the start of breeding is probably less affected by climate change than the timing of spring migration, documented by European ornithological stations.