Sheep in wolf's clothing: host nestling vocalizations resemble their cowbird competitor's

Pagnucco, Katie S.; Zanette, Liana; Clinchy, Michael; Leonard, Madeleine

doi:10.1098/rspb.2007.1706

Cited by 23 publications

(36 citation statements)

References 28 publications

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“…Such overall increase in begging intensity in crossfostered Screaming Cowbird nestlings could help explain the differences in minimum frequency and Latency ( bandwidth between them and Baywing-reared nestlings by the age of 8-10 days. In the Song Sparrow Melospiza melodia, a common host of the Brown-headed Cowbird Molothrus ater, nestlings increased the frequency and amplitude of their begging calls at parasitized nests, which would allow them to better cope with competition with cowbird nestlings for parental feedings (Pagnucco et al 2008, Boncoraglio et al 2009). Interestingly, however, adult Baywings responded similarly to begging calls of cross-fostered and Baywing-reared Screaming Cowbird nestlings, suggesting that the acoustic cues for offspring recognition remained unaffected despite the observed differences in call structure.…”

Section: Discussionmentioning

confidence: 99%

Innate development of acoustic signals for host parent–offspring recognition in the brood‐parasitic Screaming CowbirdMolothrus rufoaxillaris

Ripari

Ursino

Reboreda

et al. 2018

Ibis

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Young birds communicate their need to parents through complex begging displays that include visual and acoustic cues. Nestlings of interspecific brood parasites must ‘tune’ into these communication channels to secure parental care from their hosts. Various studies show that parasitic nestlings can effectively manipulate host parental behaviour through their begging calls, but how these manipulative acoustic signals develop in growing parasites remains poorly understood. We investigated the influence of social experience on begging call development in a host‐specialist brood parasite, the Screaming Cowbird Molothrus rufoaxillaris. Screaming Cowbird nestlings look and sound similar to those of the primary host, the Greyish Baywing Agelaioides badius. This resemblance is likely to be adaptive because Baywings discriminate against fledglings unlike their own and provision nests at higher rates in response to Baywing‐like begging calls than to non‐mimetic begging calls. By means of cross‐fostering and playback experiments, we tested whether the acoustic cues that elicit recognition by Baywings develop innately in Screaming Cowbird nestlings or are acquired through social experience with host parents or nest mates. Our results suggest that begging call structure was partially modulated by experience because Baywing‐reared Screaming Cowbird and host nestlings were acoustically more similar as age increased, whereas acoustic similarity between cross‐fostered and Baywing‐reared Screaming Cowbird nestlings decreased from 4–5 to 8–10 days of age. Cross‐fostered Screaming Cowbirds developed begging calls of lower minimum frequency and broader bandwidth than those of Baywing‐reared Screaming Cowbirds by the age of 8–10 days. Despite the observed differences in begging call structure, however, adult Baywings responded similarly to begging calls of 8‐ to 10‐day‐old cross‐fostered and Baywing‐reared Screaming Cowbirds, suggesting that these were functionally equivalent from the host's perspective. These findings support the idea that, although rearing environment can influence certain begging call parameters, the acoustic cues that serve for offspring recognition by Baywings develop in young Screaming Cowbirds independently of social experience.

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Section: Discussionmentioning

confidence: 99%

Innate development of acoustic signals for host parent–offspring recognition in the brood‐parasitic Screaming CowbirdMolothrus rufoaxillaris

Ripari

Ursino

Reboreda

et al. 2018

Ibis

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“…This is the same site where the experiments described in Pagnucco et al . () and Zanette et al . () were conducted.…”

Section: Methodsmentioning

confidence: 85%

“…Specifically, we followed the experimental protocols of Pagnucco et al . () and Zanette et al . (), but instead of experimentally parasitizing host nests with a Cowbird chick, we used a conspecific that was as large as a Cowbird chick.…”

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confidence: 85%

“…, Dearborn , Pagnucco et al . ). Of all hosts examined to date, the contrast is greatest between the Cowbird nestlings’ vocalizations and those of Song Sparrow nestlings (Briskie et al .…”

mentioning

confidence: 97%

“…, Pagnucco et al . ). Thus, Song Sparrow nestlings could be particularly vulnerable to this or some other specialized trait of the Cowbird nestling, leading to male‐biased sex ratios in this host.…”

mentioning

confidence: 97%

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Brood parasitism causes female‐biased host nestling mortality regardless of parasite species

Decaire

Zanette

Clinchy

2013

Ibis

Self Cite

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Inequality in male and female numbers may affect population dynamics and extinction probabilities and so has significant conservation implications. We previously demonstrated that Brown‐headed Cowbird Molothrus ater brood parasitism of Song Sparrows Melospiza melodia results in a 50% reduction in the proportion of female host offspring by day 6 post‐hatch and at fledging, which modelling demonstrated is as significant as nest predation in affecting demography. Many avian brood parasites possess special adaptations to parasitize specific hosts so this sex‐ratio effect could be specific to the interaction between these two species. Alternatively, perturbations associated with brood parasitism per se (e.g. the addition of an extra, larger, unrelated nestling), rather than a Cowbird nestling specifically, may be responsible. We experimentally eliminated the effects of Cowbird‐specific traits by parasitizing nests with a conspecific nestling rather than a Cowbird, while otherwise emulating the circumstances of Cowbird parasitism by adding an extra, larger (2‐day‐older), unrelated Song Sparrow nestling to Song Sparrow nests. Our parasitism treatment led to few host offspring deaths and no evidence of male‐biased sex ratios by day 6 post‐hatch. However, after day 6, female nestling mortality rates increased significantly in experimentally parasitized nests, resulting in a 60% reduction in the proportion of females fledging. Cowbird‐specific traits are thus not necessary to cause female‐biased host nestling mortality and far more general features associated with Cowbird parasitism instead appear responsible. Our results suggest, however, that Cowbird‐specific traits may help accelerate the pace of female host deaths. The conservation implications of our results could be wide reaching. Cowbirds are unrelated to all their hosts, are larger than the great majority, and a Cowbird nestling's presence can mean there is an extra mouth to feed. Thus, sex‐biased mortality in parasitized nests could be occurring across a range of host species.

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Fear affects parental care, which predicts juvenile survival and exacerbates the total cost of fear on demography

Dudeck

Clinchy

Allen

et al. 2017

Ecology

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Abstract. Fear itself (perceived predation risk) can affect wildlife demography, but the cumulative impact of fear on population dynamics is not well understood. Parental care is arguably what most distinguishes birds and mammals from other taxa, yet only one experiment on wildlife has tested fear effects on parental food provisioning and the repercussions this has for the survival of dependent offspring, and only during early-stage care. We tested the effect of fear on late-stage parental care of mobile dependent offspring, by locating radio-tagged Song Sparrow fledglings and broadcasting predator or non-predator playbacks in their vicinity, measuring their parent's behavior and their own, and tracking the offspring's survival to independence. Fear significantly reduced late-stage parental care, and parental fearfulness (as indexed by their reduction in provisioning when hearing predators) significantly predicted their offspring's condition and survival. Combining results from this experiment with that on early-stage care, we project that fear itself is powerful enough to reduce late-stage survival by 24%, and cumulatively reduce the number of young reaching independence by more than half, 53%. Experiments in invertebrate and aquatic systems demonstrate that fear is commonly as important as direct killing in affecting prey demography, and we suggest focusing more on fear effects and on offspring survival will reveal the same for wildlife.

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Sheep in wolf's clothing: host nestling vocalizations resemble their cowbird competitor's

Cited by 23 publications

References 28 publications

Innate development of acoustic signals for host parent–offspring recognition in the brood‐parasitic Screaming CowbirdMolothrus rufoaxillaris

Innate development of acoustic signals for host parent–offspring recognition in the brood‐parasitic Screaming CowbirdMolothrus rufoaxillaris

Brood parasitism causes female‐biased host nestling mortality regardless of parasite species

Fear affects parental care, which predicts juvenile survival and exacerbates the total cost of fear on demography

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