Host Use by Generalist and Specialist Brood-Parasitic Cowbirds at Population and Individual Levels

Mársico, María Cecilia de; Mahler, Bettina; Chomnalez, Manuela; Giácomo, Alejandro G. Di; Reboreda, Juan C.

doi:10.1016/s0065-3454(10)42003-3

Cited by 22 publications

(24 citation statements)

References 81 publications

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“…Screaming cowbirds and shiny cowbirds are year-round residents in the area and annually parasitize roughly 91-97% and 7-25% of baywing nests, respectively [33]. The screaming cowbird is the most specialized parasitic cowbird with only three known host species so far; it parasitizes almost exclusively the baywing in most of its geographical range [25,34]. By contrast, the shiny cowbird parasitizes more than 200 species throughout its distribution and uses baywings as secondary hosts [4,25].…”

Section: Methodsmentioning

confidence: 99%

Host–parasite coevolution beyond the nestling stage? Mimicry of host fledglings by the specialist screaming cowbird

2012

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Egg mimicry by obligate avian brood parasites and host rejection of non-mimetic eggs are well-known textbook examples of host-parasite coevolution. By contrast, reciprocal adaptations and counteradaptations beyond the egg stage in brood parasites and their hosts have received less attention. The screaming cowbird (Molothrus rufoaxillaris) is a specialist obligate brood parasite whose fledglings look identical to those of its primary host, the baywing (Agelaioides badius). Such a resemblance has been proposed as an adaptation in response to host discrimination against odd-looking young, but evidence supporting this idea is scarce. Here, we examined this hypothesis by comparing the survival rates of young screaming cowbirds and non-mimetic shiny cowbirds (Molothrus bonariensis) cross-fostered to baywing nests and quantifying the similarity in plumage colour and begging calls between host and cowbird fledglings. Shiny cowbirds suffered higher post-fledging mortality rates (83%) than screaming cowbirds (0%) owing to host rejection. Visual modelling revealed that screaming cowbirds, but not shiny cowbirds, were indistinguishable from host young in plumage colour. Similarly, screaming cowbirds matched baywings' begging calls more closely than shiny cowbirds. Our results strongly support the occurrence of host fledgling mimicry in screaming cowbirds and suggest a role of visual and vocal cues in fledgling discrimination by baywings.

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Section: Methodsmentioning

confidence: 99%

Host–parasite coevolution beyond the nestling stage? Mimicry of host fledglings by the specialist screaming cowbird

2012

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“…At our study site, we did not record any case of Shiny Cowbird parasitism in both hosts, although Shiny Cowbirds are abundant and heavily parasitize Rufous Horneros, Golden-winged Caciques, and Chalk-browed Mockingbirds (Di Giacomo 2005, De Mársico et al 2010a). This suggests that interspecific competition between parasites may be another selective force underlying host specialization in Screaming Cowbirds.…”

Section: Discussionmentioning

confidence: 77%

Reproductive success of the specialist brood parasite Screaming Cowbird in an alternative host, the Chopi Blackbird

Giácomo¹,

Reboreda

2015

The Auk

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The Screaming Cowbird (Molothrus rufoaxillaris) is the most specialized brood-parasitic cowbird, relying almost entirely on the Bay-winged Cowbird (Agelaioides badius) as host. Recently, Screaming Cowbirds have expanded their range to areas where Bay-winged Cowbirds are absent, and they are exploiting the Chopi Blackbird (Gnorimopsar chopi). Interactions between Screaming Cowbirds and Chopi Blackbirds are largely unexplored, as is the reproductive success of the parasite in this host. Screaming Cowbirds, Chopi Blackbirds, and Bay-winged Cowbirds coexist in northeastern Argentina, providing an ideal system to explore interactions between a specialist brood parasite and an alternative host and to compare the reproductive success of the parasite in its main host and in an alternative host. Screaming Cowbirds parasitized both hosts throughout their breeding seasons (Chopi Blackbirds, mid-October to mid-January; Bay-winged Cowbirds, mid-November to mid-March). Frequency of parasitism was lower in Chopi Blackbirds than in Bay-winged Cowbirds (46% vs. 74%). Nest survival was higher in Chopi Blackbirds than in Bay-winged Cowbirds (37% vs. 15%). In successful nests, survival of Screaming Cowbird eggs and chicks was high and relatively similar in both hosts (Chopi Blackbirds: eggs, 99%; chicks, 90%; Bay-winged Cowbirds: eggs, 93%; chicks, 93%), but hatchability was lower in Chopi Blackbirds than in Bay-winged Cowbirds (52% vs. 92%). Considering (1) nest survival and (2) egg survival, hatchability, and chick survival in successful nests, the reproductive success of Screaming Cowbirds (i.e. proportion of eggs that resulted in fledglings) was 0.17 in Chopi Blackbirds and 0.12 in Bay-winged Cowbirds. Our results indicate that the Chopi Blackbird is a frequent host of the Screaming Cowbird, and parasitism of this alternative host may help explain the range expansion of this parasite in areas of Brazil where the Bay-winged Cowbird is absent.Keywords: brood parasitism, Gnorimopsar chopi, host use, Molothrus rufoaxillariś Exito reproductivo del parasito de cría especialista Molothrus rufoaxillaris en un hospedador alternativo, Gnorimopsar chopi RESUMENMolothrus rufoaxillaris es el tordo parásito de cría con mayor grado de especialización y depende casi exclusivamente de Agelaioides badius como hospedador. Recientemente M. rufoaxillaris ha expandido su rango hacia áreas en las que A. badius está ausente y la evidencia indica que estarían utilizando a Gnorimopsar chopi como hospedador. Las interacciones entre M. rufoaxillaris y G. chopi son mayormente desconocidas así como eléxito reproductivo del parásito en este hospedador. Las tres especies (M. rufoaxillaris, G. chopi y A. badius) coexisten en el NE de Argentina, ofreciendo un sistema ideal para explorar las interacciones entre un parásito de cría especialista y un hospedador alternativo y para comparar eléxito reproductivo del parásito en sus hospedadores principal y alternativo. M. rufoaxillaris parasitó a ambos hospedadores a lo largo de sus temporadas reproductivas (...

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“…The frequency of parasitism is 80–90% and most nests are parasitized multiple times (Mason , Fraga , De Mársico et al . ). Greyish Baywings rarely build their own nests.…”

Section: Methodsmentioning

confidence: 97%

Roosting behaviour is related to reproductive strategy in brood parasitic cowbirds

Scardamaglia

Kacelnik

Reboreda

2018

Ibis

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Shiny Cowbirds Molothrus bonariensis and Screaming Cowbirds Molothrus rufoaxillaris are closely related brood parasites but the former is socially polygynous or promiscuous and an extreme host generalist, whereas the latter is socially monogamous and parasitizes almost exclusively one host. Females of both species lay in relative darkness, before dawn, relying for host nest location on previous days’ prospecting activity, or possibly on following better‐informed roost associates. We studied the temporal and spatial patterns of roosting behaviour in these species to test the hypothesis that roosting behaviour of cowbirds is related to their breeding strategy (brood parasitism) and reflects differences in strategies between species. We recorded fidelity to a roost, location fidelity within a roost, inter‐individual spatial associations and timing of roost departures and parasitic events, using tagged individuals. Female Shiny Cowbirds and both sexes of Screaming Cowbirds showed marked fidelity in roosting location, and roost departures occurred both during and after the known time window for parasitism, with earlier departures probably corresponding to laying days. Screaming Cowbird females and males that were trapped together and showed high levels of association during the day, also showed high levels of association in the roost. We describe the spatial and temporal patterns of a relatively poorly known aspect of avian ecology in general and the behaviour of brood parasites in particular.

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Host Use by Generalist and Specialist Brood-Parasitic Cowbirds at Population and Individual Levels

Cited by 22 publications

References 81 publications

Host–parasite coevolution beyond the nestling stage? Mimicry of host fledglings by the specialist screaming cowbird

Host–parasite coevolution beyond the nestling stage? Mimicry of host fledglings by the specialist screaming cowbird

Reproductive success of the specialist brood parasite Screaming Cowbird in an alternative host, the Chopi Blackbird

Roosting behaviour is related to reproductive strategy in brood parasitic cowbirds

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