Mixed clutches of Pied Flycatcher Ficedula hypoleuca, Blue Tit Parus caeruleus, and Great Tit P. major

Abstract

In this journal it has been stated that mixed clutches (two species laying eggs in the same nest) among cavity-nesting species often occur and often have been reported (Merilä 1994, Petrassi et al. 1998). In contrast to this, I consider the phenomenon rare, at least in the Nordic countries. In the literature, I have found only occasional reports. In this note I add three cases of mixed clutches, all from the province of Värmland: Great Tit and Pied Flycatcher, Blue Tit and Great Tit, and Blue Tit and Pied Flycatcher. To my knowledge, a mixed clutch between Blue Tit and Pied Flycatcher has not been reported earlier. Young of both species were hatched in all tree cases. These three mixed clutches are the only ones that I have recorded in spite of forty years of nest box studies, involving inspection of 3691 clutches of the three species.