Adjustments to parental care by the European Starling (Sturnus vulgaris): the effect of female condition.

Jane C. Doe and Robert K. Brown (David L. Lack), Department of Animal Ecology, College of Science.

Every organism has limited energy to expend on growth, personal maintenance, and reproduction.  At sexual maturity, life history theory predicts a trade-off will exist between self-maintenance and investment in offspring.  We examined the extent to which a decrease in female body condition affected male and female parental care in a population of European Starlings (Sturnus vulgaris).  By clipping wing and tail feathers of females to reduce their foraging ability, we predicted female parental care would decrease, and male parental care would increase in compensation.  Young reared in experimental nests fledged at significantly lower masses than those raised at control nests.  This suggests that females compensated for their handicapped condition by decreasing reproductive energy expenditure, possibly by changing foraging strategy from prey of higher quality to prey of higher availability, or by decreasing prey load per feeding trip.  Visitation rates by both parents at experimental nests tended to be slightly lower than those at control nests, though this difference was not statistically significant.  Clipped females did not lose more body mass than control females during the reproductive season, indicating that females were not willing to overcompensate for the increase in cost of reproduction.