Abstracts » Zoology and wildlife conservation

Shiny cowbirds follow the 'shotgun' strategy of brood parasitism

Article Abstract:

Whether cowbirds synchronize their egg laying with the host's laying period, and if they have mechanisms to avoid competition with other cowbird females were determined. Shiny cowbirds (Molothrus bonariensis) rely more on high fecundity and chance than on precise placement of each egg in laying their eggs in host nests. This 'shotgun' strategy, however, was possible only in house wrens (Troglodytes aedon) for wrens do not reject cowbird eggs. Shiny cowbirds monitored house wren's nests during early and late nest building and also during egg-laying stages.

Nest building, Host-parasite relationships

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Reanalysis gives further support to the 'shotgun' model od shiny cowbird parasitism of house wren nests

Article Abstract:

A study by P.E. Lowther on the nest selection of the brown-headed cowbird, M. ater, is flawed because of the procedure in which the Poisson distribution was used to test the shotgun model of brood parasitism. Data from the study of shiny cowbirds', Molothrus bonariensis, brood parasitic use on the nests of house wrens were reexamined using truncated Poisson distribution to determine the feasibility of the shotgun model. Results showed that the model is valid and can be applied to the behavior of brown-headed cowbird, M. ater.

Models, Animal behavior

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Spatial patterns of shiny cowbird brood parasitism on chestnut-capped blackbirds

Article Abstract:

A study was conducted on the spatial patterns of brood parasitism by shiny cowbirds (Molothrus bonariensis) on chestnut-capped blackbirds (Agelaius ruficapillus). Results reveal that several eggs are laid by brood parasites in the same colony and often in the same nests. Results also indicate that all morphs of cowbird eggs are accepted by chestnut-capped blackbirds. The white morphs' adaptive maintenance, however, remains unexplained.

Fringillids, Fringillidae

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