Prehatching maternal investment and offspring immunity in the pied flycatcher (Ficedula hypoleuca)

Maternal investment in offspring immunity via egg quality may be an adaptive evolutionary strategy shaped by natural selection. We investigated how maternal investment in eggs can influence offspring immunity by conducting two experiments. First, we manipulated foraging performance of the mothers before egg laying by attaching a small weight to their back feathers. During the nestling period, we investigated offspring total antibody production at the age of 7 days and after antibody challenge, and conducted a partial cross-fostering design to separate the effects of the experiment and rearing-related variation on offspring immunity. In a separate experiment, partial cross-fostering with antibody challenging without female pied flycatcher manipulation was conducted for another set of nests. Total antibody levels at the age of 7 days were reduced in nestlings of the experimental female pied flycatchers when compared with the set of unmanipulated nests. Maternal investment in the eggs may affect some aspects of offspring immunity during the early nestling period and this investment is costly. However, antibody response to a set of novel antigens (sheep red blood cells) at the end of the nestling period was not affected by the female pied flycatchers treatment. Instead our results suggest that general antibody responsiveness is mainly determined by the rearing environment and total antibody levels before the injection.