Proximate factors affecting egg volume in subarctic hole-nesting passerines

Abstract

Variation in egg volume of the Pied Flycatcher (Ficedula hypoleuca, n = 292 clutches), Redstart (Phoenicurus phoenicurus, n = 94), Siberian Tit (Parus cinctus, n = 31) and Great Tit (Parus major, n = 20) was studied in northern Finnish Lapland (69°N)from 1975 to 1987 . Increased female mass and warm temperature around the time of egg-laying increased egg volume. Egg volume was not related to laying date and clutch size .