The role of vegetation in cowbird parasitism of yellow warblers

Product Type: Book, Pages in

Year: 2000

Author(s): Howe, W.H., and F.L. Knopf

Suggested Citation:
Howe, W.H., and F.L. Knopf. 2000. The role of vegetation in cowbird parasitism of yellow warblers. In: J.N.M. Smith, T.L. Cook, S.I. Rothstein, S.K. Robinson, and S.G. Sealy (eds.). Ecology and management of cowbirds and their hosts: studies in the conservation of North American passerine birds. Austin, TX: University of Texas Press. p. 200-203.

Abstract

We studied the effects of fire on parasitism of Yellow Warbler nests by Brown-headed Cowbirds. Half of a 67-ha plot of riparian habitat in northern Colorado burned in the spring of 1989. The fire reduced the abundance of Yellow Warbler territories by nearly half, while numbers remained unchanged on the unburned area. Contrary to our expectation, we found that parasitism rates were lower on the burned area in 1989 and 1990 than in 1988. even though there was little cover for warbler nests there. and numbers of cowbird detections there did not decline after the burn. Nest predation increased on both areas after the bum, and Yellow Warblers reproduced poorly in both 1989 and 1990. We suggest that cowbirds switched from using Yellow Warblers to ground-nesting hosts with better-concealed nest sites after the burn. We speculate that cowbirds first chose host habitats by the condition of the local vegetation and then searched selectively for host nests there.