Blood Parasites of Blue-winged Teal ( Anas discors ) from Two Migratory Corridors, in the Southern USA.

We collected 180 Blue-winged Teal ( Anas discors ) in September and October 2002 from Florida, US (n=100, representing the eastern migratory corridor) and the Louisiana-Texas, US, border (n=80, representing the western migratory corridor) and examined for blood parasites using thin heart-blood smears. Leucocytozoon simondi, Haemoproteus nettionis, and microfilariae were found in 16, 23, and 27 birds, respectively. Prevalence of L. simondi and H. nettionis did not vary by migratory corridor, but the prevalence of microfilariae was higher in the western corridor (23%) than the eastern corridor (9%). No differences in prevalence of L. simondi, H. nettionis, and microfilariae were observed by host age or sex. The mean density of L. simondi and H. nettionis averaged 1.5±0.3 and 2.3±0.4 (±SE per 3,000 erythrocytes), respectively. Ranked abundance models for main and interactive effects of corridor, age, and sex were not statistically significant for L. simondi or H. nettionis. Low prevalence and abundance of hematozoa in early autumn migrants reflects the likelihood of low exposure probabilities of Blue-winged Teal on the breeding grounds, compared to their congeners.