ECOLOGY OF PARASITISM OF BROWN-HEADED COWBIRDS BY HEMATOZOA

Citation
Pj. Weatherhead et Gf. Bennett, ECOLOGY OF PARASITISM OF BROWN-HEADED COWBIRDS BY HEMATOZOA, Canadian journal of zoology, 70(1), 1992, pp. 1-7
Citations number
22
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Zoology
Journal title
ISSN journal
0008-4301
Volume
70
Issue
1
Year of publication
1992
Pages
1 - 7
Database
ISI
SICI code
0008-4301(1992)70:1<1:EOPOBC>2.0.ZU;2-P
Abstract
We quantified haematozoa infections in 964 Brown-headed Cowbirds (Molo thrus ater) sampled over three summers in eastern Ontario. Our objecti ve was to use the cowbird-haematozoa system to assess practical and th eoretical aspects of testing Hamilton and Zuk's parasite hypothesis of sexual selection. We found that most individuals resampled within and between years were consistently scored as parasitized or unparasitize d. although some individuals changed status, including going from para sitized to unparasitized. Many hatching-year birds were parasitized, w hich suggests substantial early exposure to parasites. Significant var iation within and between years in general parasite prevalence, specif ic parasite prevalence, and intensity of infections indicated that pop ulation estimates of parasitism would be highly dependent on when bird s were sampled and on the age and sex composition of the sample. Analy sis of body condition and within-season recapture patterns indicated t hat parasitism did not have a negative effect on the health of cowbird s. Parasitized birds were also recaptured at the same rate as unparasi tized birds between years, indicating that there were no viability eff ects due to parasitism. Our results suggest a number of pitfalls, some of which are potentially critical, to using haematozoa infections in passerines to test the Hamilton and Zuk hypothesis.