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

Illinois Natural History Survey, 607 East Peabody Drive, Champaign, IL 61820, USA.
Oecologia (Impact Factor: 3.09). 09/2006; 149(1):165-73. DOI: 10.1007/s00442-006-0424-1
Source: PubMed


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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Available from: Matthew J. Reetz, Sep 30, 2015
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    • "On average, female cowbirds remove a single prothonotary warbler egg from about 60% of nests that are parasitized in our study system and cowbird nestlings increase host offspring mortality, ultimately reducing the number of warblers fledging (Hoover 2003c). In prothonotary warbler nests, cowbird nestlings increase the rate of food provisioning by adult warblers (Hoover and Reetz 2006) and, weigh on average 2–3 times more than warbler nestlings (Hoover 2003c). Each year, approximately 1500 nest-boxes (1.9-L cardboard milk carton; 95 × 95 × 200 mm) were placed 40–50 m apart within appropriate habitat in approximately 20 study sites. "
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    ABSTRACT: Host manipulation by parasites is generally regarded as a classic example of the extended phenotype, where selection favors parasite genes that adaptively alter their host’s phenotype. However, selection would simultaneously favor both hosts that recoup some fitness lost to infection (i.e., compensation) and the parasites that enhance transmission by exploiting the host’s compensatory responses. Using a long-term study (19 years) of an avian brood parasite system, we demonstrate that female prothonotary warblers Protonotaria citrea compensate for partial fecundity reduction during their first brood by initiating a second breeding attempt (i.e., double-brooding). Similarly, in successful nests with naturally reduced fecundity as a result of brood parasitism, we show that being parasitized also stimulates a compensatory double-brooding response, where female warblers raising at least 1 brown-headed cowbird Molothrus ater offspring are more likely to initiate a second brood when compared with successful nonparasitized first broods. In support of the “exploitation of compensatory responses” hypothesis, parasitized females are often parasitized again in their second brood, thereby providing additional fitness benefits to cowbirds while enabling parasitized warblers that double-brood to recoup some fitness lost in the first brood. Experimentally parasitized female warblers exhibited a similar increase in double-brooding behavior, and the double-brooding frequency of parasitized female warblers was not attributable to reduced post-fledgling survival of cowbirds, thereby supplying further support for the role of parasite-induced fecundity reduction in the compensatory double-brooding behavior of a host.
    Behavioral Ecology 01/2015; 26(1-1):255-261. DOI:10.1093/beheco/aru187 · 3.18 Impact Factor
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    • ", Acadian flycatcher and wood thrush ; Rodewald and Bakermans , 2006 ) had the highest rates of nest survival . Although brood parasitism can affect population dynamics of host species ( Hoover and Reetz , 2006 ; Small et al . , 2007 ) , it was not a likely driver of urban - associated population changes for most of our focal species , with the exception of Acadian flycatcher . "
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    ABSTRACT: In contrast to the well-documented changes in avian community structure in urbanizing areas, the demographic consequences of urbanization remain less understood. As such, we examined the extent to which an urbanizing landscape matrix affected avian reproductive performance in forests. From 2001 to 2011, we studied five songbird species in 19 forested sites in Ohio, USA and monitored 4264 natural nests to determine rates of daily nest survival and brood parasitism by brown-headed cowbirds (Molothrus ater). We also tracked the annual number of fledglings produced by color-banded pairs of two focal species, the synanthropic northern cardinal (Cardinalis cardinalis, n = 974 breeding pairs between 2003 and 2011) and the urban-avoiding Acadian flycatcher (Empidonax virescens, n = 350 breeding pairs between 2001 and 2011). Over the 10-year period, neither daily nest survival nor brood parasitism rates in remnant forests were consistently related to the amount of urbanization in the surrounding landscape matrix for focal species, with the sole exception of Acadian flycatcher for which the percentage of nests with brood parasitism increased with urbanization. Annual reproductive output of cardinals was comparable across the rural–urban gradient, but Acadian flycatchers produced fewer fledglings as urbanization increased. These findings demonstrate that urban-associated patterns of annual reproduction cannot necessarily be inferred from nest survival data alone. Moreover, we show that avian community changes are not the simple consequence of nest predation. Understanding ecological processes that operate within metropolitan areas is critical if we are to conserve biological diversity on our urbanizing planet.
    Biological Conservation 04/2013; 160:32–39. DOI:10.1016/j.biocon.2012.12.034 · 3.76 Impact Factor
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    • "Evidence of carry-over effects from brood parasitism in hosts is inconsistent and likely species-specific. For example, prothonotary warbler hosts of a non-evictor parasite have reduced offspring recruitment and lower return rates (Hoover and Reetz, 2006), whereas parasitized black phoebe hosts show no reduction in subsequent clutch size (Hauber, 2006). Investigations like ours of hormonal stress response may serve to further our understanding of the costs of brood parasitism. "
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    ABSTRACT: Although models of co-evolution between brood parasites and their hosts primarily focus upon the cost to hosts in the current reproductive bout, the impact of brood parasitism may carry-over to future reproductive attempts by altering resource allocation. Glucocorticoid stress hormones help mediate resource allocation to reproduction, yet they have rarely been examined in brood parasitic systems. Here we determined if shifts in parental care and corticosterone had carry-over effects on future reproductive effort in the rufous-and-white wren (Thryophilus rufalbus), a host of the Central American striped cuckoo (Tapera naevia). We found that parasitized parents had significantly higher stress-induced, but not baseline, corticosterone than natural parents during the fledgling stage, which was associated with changes in parental care. The high investment in current reproduction while parasitized may be due to the value of fledged chicks in tropical systems. This maladaptive response by parasitized parents was associated with delayed re-nesting and a reduced likelihood of nesting in the subsequent breeding season. Although a reduction in future reproductive effort can result from a combination of factors, this work suggests that fitness costs of brood parasitism are mediated by changes in corticosterone and parental care behavior that carry-over into subsequent breeding seasons.
    Hormones and Behavior 03/2013; 63(5). DOI:10.1016/j.yhbeh.2013.03.008 · 4.63 Impact Factor
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