EN
We studied blood parasites in wild birds within Hitoy Cerere Biological Reserve and Barbilla National Park in Costa Rica during the rainy season of 2004. We examined blood samples from 248 and 114 birds, respectively. Protozoan parasites of the genus Haemoproteus as well as microfilariae were found. Prevalence of Haemoproteus in birds was 0.8% and 4.4% in Hitoy Cerere and Barbilla, respectively, and differences were significant. Prevalence of infection by microfilariae was 8.1% and 3.5%, respectively, however, differences were not significant. Based on morphological characteristics, we divided microfilariae into two groups and nine morphotypes. In Hitoy Cerere, there were microfilariae of all nine morphotypes whereas in Barbilla we only found two morphotypes.