Ankomstdatum 1948—2006 och häckning 1978—2006 i Jämtland för svartvit flugsnappare Ficedula hypoleuca, rödstjärt Phoenicurus phoenicurus och lövsångare Phylloscopus trochilus

Abstract

First arrival date of Pied Flycatcher Ficedula hypoleuca, Redstart Phoenicurus phoenicurus, and Willow Warbler Phylloscopus trochilus did not change in the province of Jämtland, Sweden (c. 63° N) during the period 1948—2006. This accords with absence of any change of April or May temperature during the same period. Breeding success was high except when the nestling period was rainy and cool (more than 3 days with rain and maximum temperature below 10° C caused severe nestling mortality). Number of Pied Flycatchers declined but high breeding success seems to exclude local factors as the cause. During the 1990s it was more difficult to get new nest-boxes occupied than it was in the 1970s (observations in other groups than those used in this study), indicating that it was the number of spring arrivals that had declined, in turn indicating that the decline may have been caused by mortality during migration or in the winter quarters.