Studies of the Age and Seasonal Variations in the Blood and Bone Marrow Parasites of a Series of Black-Billed Magpies

Abstract

Reports of the blood parasites of birds are extensive. According to Manwell (1955a), however, there have been very few attempts to study the relative incidence of iialaria and other protozoan infections of the blood in juveniles, or to discover seasonal variations in the incidence of such infections. Herman (1938) reported on the incidence of Haemoproteus in some juvenile and adult chipping sparrows. Manwell (1955b) compared the blood parasites of juvenile and adult robins from New York State and the high Rockies. Coatney and Jellison (1940), Wagner (1946), and Hagen and Olsen (1957), all reported on the hematozoa of black-billed magpies of various age levels. None of these authors, however, too clearly defined the age implications of such terms as nestling, fledgling, juvenile, iimmature, and adult. In a very extensive study of the plasmodia of Kern Co., Calif., birds, Herman et al (1954) noted the organisms in three welldefined age groups of 3 species of birds. Similar observations on the parasites of Canada geese in specific age categories were made by Levine and Hanson (1953), Wehr and Herman (1954), and Hanson et al (1956). Even less has been published on seasonal variations in parasite incidence. Jordan (1943) noted some seasonal influence on Haemoproteus and malaria infections in 3 species of birds. MAanwell (1955a) noted seasonal incidence of blood parasites in the song sparrow. Considerable year-to-year incidence data were reported by Herman et al (1954). The writer has accumulated data relative to