ATWELL, J.W.*; BOUGHTON, R.K.; SCHOECH, S.J.; Indiana Univ.*; Univ. of Memphis: THE EFFECTS OF AN ECTOPARASITE ON IMMUNE FUNCTION, STRESS RESPONSE, AND SURVIVAL OF FLORIDA SCRUB-JAYS

In long-lived iteroparous organisms that delay reproduction, life-history theory predicts the evolution of strong host responses to parasite infestation that will maximize lifetime reproductive success. While the effects of parasitism on nestling birds have been well studied, the physiological responses of free-living adult and sub-adult birds to parasites have received less attention. We report on the effects of an introduced generalist ectoparasite, the sticktight flea (Echidnophaga gallinacea), on the physiology of Florida Scrub-Jays (Aphelocoma coerulescens). We compared flea-infested and non-infested birds, controlling for sex and age. For most jays, before and after infestation data allowed us to assess changes across time. Adult flea-infested jays lost more body mass than non-infested jays during the previous year, and first-year jays with fleas gained body mass at a slower rate. Similarly, flea-infested jays had lower hematocrit (as low as 16%) than non-infested jays, and decreases in hematocrit were greater for flea-infested jays. Body mass changes, hematocrit, and changes in hematocrit were negatively correlated with infestation level. Paradoxically, whereas leukocyte counts and heterophil-lymphocyte ratios were higher in infested jays, plasma immunoglobulin (IgG) levels were lower and negatively correlated with infestation level. Although neither baseline plasma corticosterone (CORT) levels nor levels induced during 30 min of capture stress differed between infested and non-infested birds, infested birds� CORT levels increased more rapidly in the first few minutes than those of non-infested jays. Of critical concern for this threatened species are the death rate data: 36.4% of the infested jays died during the one year study as compared to 5.9% of the non-infested jays.