Do parasitic mites decrease growth of nestling Pied Flycatchers Ficedula hypoleuca?

The effect of a parasitic mite Dermanyssus hirundinis on the growth and survival of nestling Pied Flycatcher Ficedula hypoleuca was tested by an experiment where the parasite level was reduced in half of the nest boxes using an insecticide, Although the abundance of mites was significantly reduced in the experimental group, there was no difference in body mass, tarsus length or fledging rate between nestlings in the experimental and the unmanipulated group. There was however a negative correlation in the unmanipulated group between body mass and mite abundance, as had also been observed in an earlier, non-experimental study (Merino and Potti 1995). I suggest that this correlation is a consequence of variation in some aspect of parental quality and not a direct effect of the parasitic mites.

Bauchau V., ARDEA 85 (2): 243-247.