AVIAN MALARIA, BODY CONDITION, AND BLOOD PARAMETERS IN FOUR SPECIES OF SONGBIRDS

摘要

Avian malaria is a common disease in songbirds, caused by protozoa in the genera Plasmodium, Haemoproteus, and Leucocytozoon. These parasites can negatively impact bird health, survival, and reproductive success. Four species of songbirds were sampled for blood parasites during the reproductive season; the American Redstart (Setophaga ruticilla), the Gray Catbird (Dumetella carolinensis), the Cedar Waxwing (Bombycilla cedrorum), and the Red-eyed Vireo (Vireo olivaceus). The study aimed to determine parasite prevalence in these species, as well as to explore a relationship between infection and bird health, measured by body condition and blood parameters. We also tested whether age and sex had an effect on this relationship. Results detected a high parasite prevalence across all species using PCR (94%) but a much lower one using microscopy (37%), suggesting that parasite prevalence is high while parasitemia is low. Red-eyed Vireos were the only species with high prevalence and parasitemia. Parasite infection did not have an effect on body condition or any of the blood parameters tested (hematocrit and heterophil/lymphocyte [H/L] ratio). Because of variation in the reproductive strategies of the targeted species, we expected to find sex-specific differences in infection and health of redstarts and vireos (females having higher parasite prevalence and more health concerns than males) but no sex-specific differences in catbirds and waxwings. We also expected to find age-specific differences in infection and health in all species (juveniles having higher parasite prevalence and more health concerns than adults). Overall, age and sex did not have an effect on infection or health in any of the species, except for infected vireos, as females had a higher H/L ratio than males. This association could be attributed to the high parasitemia found exclusively in vireos. Time was tested as an additional factor and revealed a trend in waxwings, showing that birds caught later in the season (breeding) had higher parasite prevalence and lower body mass, hematocrit, and H/L ratio than birds caught earlier in the season (pre-breeding), consistent with infection by Leucocytozoon.