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Providing evidence to improve practice

Individual study: Impact of control of brown-headed cowbirds Molothrus ater on the breeding success of Kirtland's warbler Dendroica kirtlandii on the Lower Peninsula, Michigan, USA

Published source details

Kepler C.B., Irvine G.W., DeCapita M.E., & (1996) The conservation management of Kirtland's warbler Dendroica kirtlandii. Bird Conservation International, 6, 11-22


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Remove/control adult brood parasites Bird Conservation

A before-and-after study in young jack pine Pinus banksiana forests in Michigan, USA (Kepler et al. 1996) found that, following the trapping and removal of a total of 84,937 brown-headed cowbirds Molothrus ater between 1972 and 1992, parasitism rates of Kirtland's warbler Dendroica kirtlandii nests by cowbirds fell significantly and productivity increased, compared to 1944-57 or 1966-71, before cowbird control was started (1944-57: 55% of 137 nests parasitised vs. 1966-71: 69% of nests parasitised, 0.8 fledglings/nest, sample size not provided; 1972-1977: 6% of 230 nests parasitised, 2.7 fledglings/nest; 1989-91: 2% of 48 nests parasitized). However, these changes did not result in increased numbers of singing males, with seasonal numbers fluctuating from 167-243 during 1971-89.