Weather and breeding success at high latitudes-the Pied Flycatcher Ficedula hypoleuca and the Siberian Tit Parus cinctus

Abstrakti

The breeding success of the migratory Pied Flycatcher (Ficedula hypoleuca) and the resident Siberian Tit (Parus cinctus) were studied during 1986-1994 in Finnish Lapland. In the Pied Flycatcher, 15% of eggs did not hatch. In spells of cold weather, during the nestling period, Pied Flycatchers tried to compensate for the inactivity of winged insects (main food items) by altering their foraging niches and diet . However, low temperatures greatly decreased the feeding frequency of the Pied Flycatcher. The incapability to feed the young in cold and rainy conditions negatively affected nestling growth and fledging success in the Pied Flycatcher. In the Siberian Tit, neither the foraging strategy, nor the feeding frequency changed in relation to temperature. The hatching success of the Siberian Tit was very good in spite of early breeding, but 22% of nestlings died during the nestling period . We could not link nestling mortality with any climatic factors.