02567nas a2200229 4500008004100000245010800041210006900149300001300218490000800231520185700239653002502096653001502121653001402136653001502150653001902165653001702184653002002201100002102221700001702242700001902259856005902278 2008 eng d00aEffects of experimental cowbird removals on brood parasitism and nest predation in a grassland songbird0 aEffects of experimental cowbird removals on brood parasitism and a820 -8300 v1253 a
Brood parasitism and predation are two factors that limit seasonal fecundity in grassland songbirds. We removed Brown-headed Cowbirds (Molothrus ater) in a switchback experiment to examine the effects of brood parasitism and nest predation on the productivity of Dickcissels (Spiza americana). Nesting Dickcissels were monitored at four study plots in northeast Kansas in a two-year study. Brown-headed Cowbirds were captured with drop-in traps at two removal plots, two unmanipulated plots were reference plots, and treatments were reversed between years. To evaluate the effect of Brown-headed Cowbird removals, we compared the percentage of nests parasitized, rates of multiple parasitism, clutch size, daily nest survival rates, and overall productivity per nest between removal and reference plots. Removals of Brown-headed Cowbirds successfully reduced the probability of parasitism and rates of multiple parasitism, but only in one of two years. Brown-headed Cowbirds did not appear to contribute to nest losses, given that few nests were abandoned because of cowbird activity and that the probabilities of nest parasitism and nest survival declined simultaneously over the breeding season. Overall, nest productivity showed no difference between treatments in either year, despite reduced rates of parasitism at removal plots in 2004. High rates of nest predation minimized the potential benefits of Brown-headed Cowbird removals for increasing productivity of Dickcissels. Our results demonstrate that removals can reduce parasitism levels but that the success of removal programs may vary annually, particularly in regions where Brown-headed Cowbirds and nest predators are abundant. Management actions that minimize parasitism and predation by modifying habitat structure may provide better alternatives to programs based on removals.
10abrown-headed cowbird10aDickcissel10afecundity10amanagement10aMolothrus ater10aproductivity10aSpiza americana1 aSandercock, B.K.1 aHewett, E.L.1 aKosciuch, K.L. uhttps://academic.oup.com/auk/article/125/4/820/514820600501nas a2200109 4500008004100000245010000041210006900141260003500210490001400245100001700259856011500276 2005 eng d00aThe effect of brown-headed cowbird removal on thedemography of the dickcissel (Spiza americana)0 aeffect of brownheaded cowbird removal on thedemography of the di aIthaca, NYbCornell University0 vBS Thesis1 aHewett, E.L. uhttp://lter.konza.ksu.edu/content/effect-brown-headed-cowbird-removal-thedemography-dickcissel-spiza-americana