Behavioral Ecology of Fledgling Brown-Headed Cowbirds and Their Hosts

Woodward, Paul W.

doi:10.2307/1367248

Cited by 51 publications

(63 citation statements)

References 18 publications

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“…To correct for biases imposed by nests found in advanced stages, we used the method of May®eld (1975) for calculating the nesting success rate for the egg-laying through¯edging periods. Because we were interested in the quality of a species as a cowbird host, average cowbird incubation and nestling time lengths, eleven and ten days, respectively, were used (Payne 1977;Woodward 1983). Two days were used for the host egg-laying period prior to the onset of incubation, for a total of 23 days from the egg-laying through thē edging period.…”

Section: Methodsmentioning

confidence: 99%

Community-wide patterns of parasitism of a host "generalist" brood-parasitic cowbird

Strausberger

Ashley

1997

Oecologia

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The brown-headed cowbird (Molothrusater) is a generalist obligate brood parasite. Despite intensive study and growing concern over the negative impact of cowbird parasitism on populations of many hosts, very little is known about the factors influencing community-wide patterns of cowbird parasitism. Using systematic nest searches, nest parasitism was studied over two breeding seasons at a study site in northeastern Illinois encompassing grassland, forest-edge, and forest habitat, supporting a diverse avian community. Parasitism was observed for 18 out of 34 altricial bird species found nesting at the study site. A total of 299 cowbird eggs and nestlings were found in 191 of a total of 593 nests. Analyses revealed several ecological and behavioral factors associated with frequency of parasitism and the resulting distribution of cowbird eggs. Much higher frequencies of parasitism were found in edge and forest habitats than in grassland. Within the edge habitat, open nests were parasitized significantly more often than cavity nests. Among open nests in the edge habitat, the two largest species were never parasitized. Host behavior, particularly egg-ejection behavior, was associated with a reduced observed frequency of parasitism, but at least three species known to eject cowbird eggs were sometimes parasitized. For six common hosts capable of rearing cowbirds, we found no correlation between level of parasitism and host nest-survivorship, suggesting that fine-grained assessments of host quality by female cowbirds do not influence patterns of parasitism among acceptable host species, or that differences in host quality are not great and/or predictable enough for such fine-grained assessments. Our results suggest that when a variety of possible nests are available, the level of parasitism on a particular species is a balance between a␣cowbird's preference for a particular species and the effectiveness of host species' defenses. A conceptual model was developed that incorporates the observed correlation of cowbird eggs or nestlings with habitat, nest-type, host species' body mass, and host behavioral defenses. Additional community-wide studies of cowbird parasitism will test if this model is applicable to other avian communities.

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Section: Methodsmentioning

confidence: 99%

Community-wide patterns of parasitism of a host "generalist" brood-parasitic cowbird

Strausberger

Ashley

1997

Oecologia

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“…Woodward (1983) summarized feeding rates (feeds per hour) to cowbirds and host Xedglings for eight parasitized host species. For all species, the feeding rate to host Xedglings with equivalent total mass of a cowbird Xedgling was signiWcantly lower than the feeding rate to a single cowbird, and the cowbirds did not become independent until they were 25-39 days old.…”

Section: Ovspring Recruitment and Juvenile Survivalmentioning

confidence: 99%

“…There is extensive evidence that parasitic brown-headed cowbird (Molothrus ater) chicks beg more intensively than their host nest-mates (Woodward 1983;Lowther 1993;Dearborn 1998;Lichtenstein and Sealy 1998), thereby elevating provisioning rates of , and energetic costs to foster parents (Kilpatrick 2002). In addition, if provisioning rates of parents do not keep up with demand, competitively inferior host nestlings may weigh less when they Xedge from parasitized broods (Smith 1981;Dearborn et al 1998;Hoover 2003a).…”

Section: Introductionmentioning

confidence: 99%

Brood parasitism increases provisioning rate, and reduces offspring recruitment and adult return rates, in a cowbird host

Hoover

Reetz

2006

Oecologia

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Interspecific brood parasitism in birds presents a special problem for the host because the parasitic offspring exploit their foster parents, causing them to invest more energy in their current reproductive effort. Nestling brown-headed cowbirds (Molothrus ater) are a burden to relatively small hosts and may reduce fledgling quality and adult survival. We documented food-provisioning rates of one small host, the prothonotary warbler (Protonotaria citrea), at broods that were similar in age (containing nestlings 8-9 days old), but that varied in composition (number of warbler and cowbird nestlings) and mass, and measured the effect of brood parasitism on offspring recruitment and adult returns in the host. The rate of food provisioning increased with brood mass, and males and females contributed equally to feeding nestlings. Controlling for brood mass, the provisioning rate was higher for nests with cowbirds than those without. Recruitment of warbler fledglings from unparasitized nests was 1.6 and 3.7 times higher than that of fledglings from nests containing one or two cowbirds, respectively. Returns of double-brooded adult male and female warblers decreased with an increase in the number of cowbirds raised, but the decrease was more pronounced in males. Reduced returns of warbler adults and recruitment of warbler fledglings with increased cowbird parasitism was likely a result of reduced survival. Cowbird parasitism increased the warblers' investment in current reproductive effort, while exerting additional costs to current reproduction and residual reproductive value. Our study provides the strongest evidence to date for negative effects of cowbird parasitism on recruitment of host fledglings and survival of host adults.

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“…In late summer, after reaching independence from their host parents, young cowbirds join flocks formed primarily of other young cowbirds (Friedmann, 1929;Woodward, 1983). Over the winter, the young cowbird is typically found in very large flocks consisting of cowbirds and other (often blackbird) species.…”

mentioning

confidence: 99%

Social transmission of courtship behavior and mating preferences in brown-headed cowbirds,Molothrus ater

Freeberg

2004

Learning & Behavior

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Behavioral Ecology of Fledgling Brown-Headed Cowbirds and Their Hosts

Cited by 51 publications

References 18 publications

Community-wide patterns of parasitism of a host "generalist" brood-parasitic cowbird

Community-wide patterns of parasitism of a host "generalist" brood-parasitic cowbird

Brood parasitism increases provisioning rate, and reduces offspring recruitment and adult return rates, in a cowbird host

Social transmission of courtship behavior and mating preferences in brown-headed cowbirds,Molothrus ater

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