Variation in the laying intervals of the Pied Flycatcher and the Redstart

Abstract

The egg-laying pattern of two nest-box breeders, the Pied Flycatcher Ficedula hypoleuca, and the Redstart Phoenicurus phoenicurus, was studied in a forested region in Finnish Lapland during 1986-1993 . Laying schedule and laying order were examined, and hatching and fledging success recorded. The coldness of the spring of 1993, caused laying gaps in the Pied Flycatcher of which the longest intervals between laying two eggs were 2x11, 2x10 and 1x9 days. Long lying of the first-laid eggs in the nest, because of laying gaps, resulted in a low hatching success for these eggs . Egg laying lasted for two or three days until the female could interrupt her egg-laying after a drastic drop in the temperature. The Redstart, unlike the Pied Flycatcher, did not respond to the exceptionally low temperatures during the time of egg-laying . The effect of the cold temperatures on the egg-laying of the Pied Flycatcher may be less than the impact due to the scarcity of food, especially flying insects.