Parental Effort and Parasite Resistance in the Red-Bellied Woodpecker (Melanerpes Carolinus)

I used a combination of observational and experimental approaches to investigate the potential for a trade-off between parental effort and parasite resistance to mediate the cost of reproduction in a population of Red-bellied Woodpeckers (Melanerpes carolinus) nesting in natural cavities in the Apalachicola National Forest in north Florida. In the observational part of this study, I examined how the prevalence of a haematozoan parasite (Haemoproteus velans) of the Red-bellied Woodpecker varies seasonally. I also investigated how infection with this parasite was associated with host mass, body condition, and overwinter survival. In the second part of this study, I used a brood manipulation experiment to test whether there is a trade-off between caring for an increased brood and resisting H. velans, and whether this trade-off is associated with a decrease in a component of residual reproductive value. The observational study was conducted between May 2000 and July 2001. Analysis of blood smears taken from individual woodpeckers during this period indicated that the prevalence of H. velans peaked during the Red-bellied Woodpecker breeding season and was lowest during the winter months. Infection with H. velans was associated with low mass and poor body condition in males. Infection showed no association with female mass. There was no statistically significant association between infection with H.velans and overwinter survival in males or females. However, males infected with H. velans tended to have lower overwinter survival than uninfected males. The brood manipulation experiment was conducted during the spring and summer of 2002. There was no effect of the brood manipulation on male feeding rates, however the prevalence of H. velans in males caring for enlarged broods tended to be higher than the prevalence in males caring for reduced or control broods. Females caring for enlarged broods made more feeding trips per hour than females caring for reduced or control broods, however there was no effect of brood manipulation on the prevalence of Haemoproteus in females. There was no effect of brood manipulation on the success of second or third broods. The results of this study suggest that there may be a trade-off between reproductive effort and resistance to Haemoproteus in Red-bellied Woodpeckers. This type of trade-off is generally thought to arise when limited energy must be partitioned between provisioning nestlings and resisting disease; however the results of this study indicate that a trade-off between caring for an enlarged brood and resisting haematozoa can arise even if parents do not increase their feeding rates. In addition, although there appears to be a trade-off between caring for an enlarged brood and resisting Haemoproteus this trade-off was not associated with a decrease in residual reproductive value, at least within one season.