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Living with Parasites: Prevalence of a Blood Parasite and Its Effect on Survivorship in the Purple Martin
Priya Davidar and Eugene S. Morton
Vol. 110, No. 1 (Jan., 1993), pp. 109-116
Published by: American Ornithological Society
Stable URL: http://www.jstor.org/stable/4088237
Page Count: 8
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We studied the prevalence of the blood parasite Haemoproteus prognei (Haematoprotozoa) from 1986 to 1990 in a breeding colony of Purple Martins (Progne subis) in Maryland and in overwintering martins in three Brazilian roosts in 1990. Yearling breeders were infected at a significantly lower rate than adults, and no yearlings in wintering roosts were infected. Haemoproteus prognei might be more virulent in immunologically naive birds and cause high mortality in young birds during the stress of their first migration. Many birds became infested over three years and most maintained a chronic infection. Infected birds returned to the colony with the same frequency as uninfected birds. Infected adults tended to arrive at the breeding site ahead of uninfected adults. Clutch size did not differ, but uninfected females had lower breeding success than infected individuals. We discuss the evolutionary implications of high mortality coupled with superior breeding success in chronically infected birds, whose immune system has been "tested" for parasite resistance, and suggest an alternative to the predominant view that parasite resistance means avoiding them altogether.
The Auk © 1993 American Ornithologists' Union