Print PageReproduction is thought to be costly, leading to a hypothesized tradeoff between investment in a current reproductive attempt and investment in self-maintenance and future reproduction. The existence of this tradeoff can best be detected by experiments that manipulate parental energy expenditures, either through directly supplementing food, changing brood size, or handicapping the parents. Estimating the eventual recruitment of offspring to the breeding population is a better evaluation of the effects of these experiments in the context of lifetime reproductive strategy than short-term measurements of investment, such as number of offspring at time of independence or body condition of offspring. We evaluated the effects of a food supplementation experiment on the long-term survival of American kestrels (Falco sparverius) that had fledged from experimental nests using Bayesian mark-recapture models.
Results/Conclusions
Although nestlings that had received the food supplement tended to fledge with higher body conditions (mass corrected by size acknowledging a scaling relationship) than control counterparts, their higher rate of survival was better explained by treatment group independent of the difference in body condition. The food supplementation process likely affected nestling survival and recruitment through mechanisms not quantified here, such as changes in parental behavior during the post-fledging period, or nutritional effects not measured by a size-corrected mass index. Our study demonstrated how the manipulation of parental investment through food supplementation might result in a long-term demographic consequence on offspring. Moreover, this difference was greatest in a year when breeding adult survival was not positively affected by the food supplement, providing support for the hypothesized tradeoff.
