caa a22 4500 465782574 CHVBK 20180323111959.0 cr unu---uuuuu 170327e19901201xx s 000 0 eng 10.1007/BF00164066 doi (NATIONALLICENCE)springer-10.1007/BF00164066 Differential parasitism of least flycatchers and yellow warblers by the brown-headed cowbird [Elektronische Daten] [James Briskie, Spencer Sealy, Keith Hobson] Summary: Brown-headed cowbirds (Molothrus ater) parasitized yellow warblers (Dendroica petechia) six times more frequently than least flycatchers (Empidonax minimus) nesting in the same riparian habitat in southern Manitoba. This difference was surprising because least flycatchers were higher quality hosts; flycatchers always accepted cowbird eggs while warblers did so on only about half the occasions. Both hosts were equally good foster parents, at least until fledging; thus, once an egg was accepted there was probably no further advantage in parasitizing one species over the other. The probability that a nest was parasitized decreased with increasing nest height, perhaps as a consequence of the cowbird's habit of searching for nests close to the ground. Since least flycatchers nested higher in the canopy than yellow warblers, a greater proportion of flycatcher nests probably were not detected by cowbirds. Nevertheless, nest height alone could not account fully for the lower incidence of parasitism on flycatchers. Clutch initiation in flycatchers peaked 6 days after warbler clutch initiations and 5 days after that of cowbirds. Despite the later peak in initiations, flycatcher nests were always available as potential hosts over the entire cowbird laying season and it was not until new clutch initiations by warblers declined in late summer that flycatchers were actually used as hosts. Because least flycatchers responded more aggressively than yellow warblers to a model female cowbird at the nest, we concluded that greater nest defense by flycatchers may have also reduced the rate of brood parasitism in this host. Together, our results suggest the large difference in the frequency of parasitism between these two hosts was primarily a product of nest location but that differences in host nest-defense and breeding season asynchrony may have contributed to preferential host selection. Springer-Verlag, 1990 Briskie James Department of Zoology, University of Manitoba, R3T 2N2, Winnipeg, Manitoba, Canada aut Sealy Spencer Department of Zoology, University of Manitoba, R3T 2N2, Winnipeg, Manitoba, Canada aut Hobson Keith Department of Zoology, University of Manitoba, R3T 2N2, Winnipeg, Manitoba, Canada aut Behavioral Ecology and Sociobiology Springer-Verlag 27/6(1990-12-01), 403-410 0340-5443 27:6<403 1990 27 265 https://doi.org/10.1007/BF00164066 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00164066 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Briskie James Department of Zoology, University of Manitoba, R3T 2N2, Winnipeg, Manitoba, Canada aut NATIONALLICENCE 700 1- Sealy Spencer Department of Zoology, University of Manitoba, R3T 2N2, Winnipeg, Manitoba, Canada aut NATIONALLICENCE 700 1- Hobson Keith Department of Zoology, University of Manitoba, R3T 2N2, Winnipeg, Manitoba, Canada aut NATIONALLICENCE 773 0- Behavioral Ecology and Sociobiology Springer-Verlag 27/6(1990-12-01), 403-410 0340-5443 27:6<403 1990 27 265 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer