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A total of 8170 birds of 153 species, representing 41 families, from Maryland and New Jersey, were examined for blood parasites. Eighty-eight species were sampled in New Jersey and 128 in Maryland; 63 species were common to both areas. Ten percent (833) of the birds harbored one or more parasite species of the following genera: Haemoproteus (4.3%), Leucocytozoon (3.9%), Plasmodium (1.9%), Trypanosoma (0.3%), Lankesterella (=Atoxoplasma) (0.04%), and unidentified microfilariae (0.3%). Prevalences from both areas were similar, but were markedly lower than previously recorded. The coefficient of community, an ecological measure of similarity, was applied to both bird and parasite faunas within the two study areas, and indicated that because of the high degree of specificity of parasites to their hosts only birds shared by the two samples had the same parasites. This measure also revealed the absolute necessity of using only similar taxa in any comparison of hematozoan prevalence in different avifaunas in different geographic regions.The Maryland sample was unique in that it allowed a comparison of prevalences over a 30-year period, revealing that years with larger samples generally exhibited a uniform geographic prevalence. The New Jersey sample was obtained from different topographic regions; the results confirm the concept that prevalence of hematozoa is correlated with regional topography, even in areas closely juxtaposed.

During 1966–69 mortality attributed to Lankesterella infections occurred among evening grosbeaks (Hesperiphona vespertina) in Algonquin Park, Ontario. Peak mortality was recorded between mid-June and mid-July in all four years, being highest in 1967. The parasite was subsequently discovered in wild rose-breasted grosbeaks (Pheucticus ludovicianus) and was artificially transmitted to other passerines (though not to a duck) by inoculating infected tissues. Mites from two infected grosbeaks failed to initiate infections when fed to uninfected birds, Isospora oocysts from the feces of grosbeaks were not infective to canaries. The ultrastructure of the parasite in grosbeaks is similar to other eimeriid coccidia. The generic nature of this parasite is discussed in light of recent reports that the species of Lankesterella (= Atoxoplasma) in house sparrows might really be referable to Isospora.