Interactions between prenatal maternal effects and posthatching conditions in a wild bird population

Resources and cues provided by the mother before birth are important mediators of developmental plasticity. It has been suggested that the adaptive value of such prenatal maternal effects may depend on the environment encountered by the offspring after birth, and that offspring may perform better when environmental conditions encountered by the mother and the offspring match, than when a mismatch occurs. Here, we test how prenatal maternal effects and postnatal conditions interact in influencing offspring growth and development in wild-living great tits (Parus major) by manipulating food availability experienced by the mother before egg laying, partially cross-fostering nestlings between nests, and manipulating food availability after hatching. We observed significant interaction effects between pre- and postnatal food conditions. Nonsupplemented nestlings reached a similar fledging mass, a trait closely linked to postfledging survival, as food-supplemented nestlings when their biological mother had received extra food during egg laying. It shows that prenatal maternal investment can compensate for growth-limiting conditions after hatching. This effect was sex specific, with daughters benefiting more than sons. Furthermore, food-supplemented nestlings grew largest when their biological mother had not received extra food during egg laying, suggesting that offspring were primed prenatally, possibly through differential egg composition, to use resources more efficiently. However, we found no evidence that offspring performed generally better when pre- and postnatal food conditions matched than when a mismatch occurred. Our results demonstrate the importance of considering the postnatal environment when testing for the ecological and evolutionary consequences of prenatal maternal effects in natural populations.Resources transferred by the bird mother via the egg help to reduce the negative consequences of a harsh environment after birth. Furthermore, mothers encountering harsh environmental conditions during egg laying prime their offspring to use available resources more efficiently later in life. Our study shows that the environment encountered before birth can have important long-term consequences on offspring performance and the way animals interact with their environment.