DERRYBERRY, E.P.*; FOUFOPOULOS, J.; DOBSON, A.P.; MACDOUGALL-SHACKLETON, E.A.; HAHN, T.P.; Duke University, Durham, NC; University of Michigan, Ann Arbor; Princeton University, NJ; University of Western Ontario, London; University of California, Davis: An investigation of the effects of two haematozoa on reproductive success in mountain white-crowned sparrows.
Blood-borne parasites may impose selective pressures on their host populations by influencing host reproductive effort and success. The cost of an infection may be a negative effect on a host’s reproductive effort and success. We studied the effects of Haemoproteus and Plasmodium on reproduction of mountain white-crowned sparrows (Zonotrichia leucophrys oriantha) breeding in the central Sierra Nevada. This population is well suited to study this effect because over 30 years of data exist on both sexes’ reproductive effort and success. During three breeding seasons (1999, 2001, 2002), we recorded the infection status and reproductive success for both parents at over 100 nests. We found a temporal fluctuation in infection prevalence, the peaks of which corresponded to particular nesting stages such as incubation and feeding of hatchlings. In one late breeding season (1999), we also found that infected females had significantly lower reproductive success than uninfected females at several different nesting stages. During the same season, nests with at least one infected parent had significantly lower success at almost all nesting stages than nests with no infected parents. Even though infected females had lower reproductive success, it did not appear to be exclusively the result of the infection itself since they had about equal chances of complete success or complete failure. We suggest that an infected female is more susceptible to external stressors and thus more likely to enter an emergency life history stage where their survival becomes the focus and other processes such as reproduction are deprioritized, often leading to their reproductive failure. This research was supported by NSF DEB-9806765.
