Study

Effect of brown-headed cowbird Molothrus ater removal on parasitism rate of hooded warbler Wilsonia citrina nests in Crawford County, Pennsylvania, USA

  • Published source details Stutchbury B.J.M. (1997) Effects of female cowbird removal on reproductive success of hooded warblers. The Wilson Bulletin, 109, 74-81

Actions

This study is summarised as evidence for the following.

Action Category

Remove/control adult brood parasites

Action Link
Bird Conservation
  1. Remove/control adult brood parasites

    A replicated, controlled before-and-after study between 1984 and 1995 at three 50-100 ha (2 experimental and 1 control) hardwood forest sites in Pennsylvania, USA (Stutchbury 1997) found that the proportion of hooded warbler Wilsonia citrina nests parasitised by brown-headed cowbirds Molothrus ater was significantly lower during years when cowbirds were removed (11% of 241 nests parasitised in 1991-5 vs. 64% of 28 nests parasitised in 1984-90). When comparing sites, parasitism rates were lower on sites with cowbird removal (0-11% of 280 nests parasitised at removal sites vs. 38-58% of 32 nests at controls). However, there were no changes in warbler nesting success between sites with low (?5%) and high (>30%) levels of parasitism (average of 1.7 fledglings/nest in sites with low parasitism vs. 1.6 fledglings/nest in sites with high parasitism). The authors suggest that nesting success may be more determined by high rates (22-52%) of predation, than by parasitism. An average of 11-20 female and 7.5-17 male cowbirds were removed each year.

     

Output references

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