Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests

Avian brood parasites usually remove or puncture host eggs. Several hypotheses have been proposed to explain the function of these behaviors. Removing or puncturing host eggs may enhance the efficiency of incubation of cowbird eggs (incubation-efficiency hypothesis) or reduce competition for food be...

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Autores principales: Astie, A.A., Reboreda, J.C.
Formato: JOUR
Materias:
Brood parasitism
Egg puncture
Molothrus bonariensis
Turdus amaurochalinus
Aves
Molothrus
Turdidae
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_02738570_v80_n4_p336_Astie
Aporte de:
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id todo:paper_02738570_v80_n4_p336_Astie
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spelling todo:paper_02738570_v80_n4_p336_Astie2023-10-03T15:15:52Z Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests Astie, A.A. Reboreda, J.C. Brood parasitism Egg puncture Molothrus bonariensis Turdus amaurochalinus Aves Molothrus Molothrus bonariensis Turdidae Turdus amaurochalinus Avian brood parasites usually remove or puncture host eggs. Several hypotheses have been proposed to explain the function of these behaviors. Removing or puncturing host eggs may enhance the efficiency of incubation of cowbird eggs (incubation-efficiency hypothesis) or reduce competition for food between cowbird and host chicks in parasitized nests (competition-reduction hypothesis) and, in nonparasitized nests, may force hosts to renest and provide cowbirds with new opportunities for parasitism when nests are too advanced to be parasitized (nest-predation hypothesis). Puncturing eggs may also allow cowbirds to assess the development of host eggs and use this information to decide whether to parasitize a nest (test-incubation hypothesis). From 1999 to 2002, we tested these hypotheses using a population of Creamy-bellied Thrushes (Turdus amaurochalinus) in Argentina that was heavily parasitized by Shiny Cowbirds (Molothrus bonariensis). We found that 56 of 94 Creamy-bellied Thrush nests (60%) found during nest building or egg laying were parasitized by Shiny Cowbirds, and the mean number of cowbird eggs per parasitized nest was 1.6 ± 0.1 (N = 54 nests). At least one thrush egg was punctured in 71% (40/56) of parasitized nests, and 42% (16/38) of nonparasitized nests. We found that cowbird hatching success did not differ among nests where zero, one, or two thrush eggs were punctured and that the proportion of egg punctures associated with parasitism decreased as incubation progressed. Thus, our results do not support the incubation-efficiency, nest-predation, or test-incubation hypotheses. However, the survival of cowbird chicks in our study was negatively associated with the number of thrush chicks. Thus, our results support the competition-reduction hypothesis, with Shiny Cowbirds reducing competition between their young and host chicks by puncturing host eggs in parasitized nests. © 2009 Association of Field Ornithologists. Fil:Astie, A.A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Fil:Reboreda, J.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_02738570_v80_n4_p336_Astie
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic Brood parasitism
Egg puncture
Molothrus bonariensis
Turdus amaurochalinus
Aves
Molothrus
Molothrus bonariensis
Turdidae
Turdus amaurochalinus
spellingShingle Brood parasitism
Egg puncture
Molothrus bonariensis
Turdus amaurochalinus
Aves
Molothrus
Molothrus bonariensis
Turdidae
Turdus amaurochalinus
Astie, A.A.
Reboreda, J.C.
Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests
topic_facet Brood parasitism
Egg puncture
Molothrus bonariensis
Turdus amaurochalinus
Aves
Molothrus
Molothrus bonariensis
Turdidae
Turdus amaurochalinus
description Avian brood parasites usually remove or puncture host eggs. Several hypotheses have been proposed to explain the function of these behaviors. Removing or puncturing host eggs may enhance the efficiency of incubation of cowbird eggs (incubation-efficiency hypothesis) or reduce competition for food between cowbird and host chicks in parasitized nests (competition-reduction hypothesis) and, in nonparasitized nests, may force hosts to renest and provide cowbirds with new opportunities for parasitism when nests are too advanced to be parasitized (nest-predation hypothesis). Puncturing eggs may also allow cowbirds to assess the development of host eggs and use this information to decide whether to parasitize a nest (test-incubation hypothesis). From 1999 to 2002, we tested these hypotheses using a population of Creamy-bellied Thrushes (Turdus amaurochalinus) in Argentina that was heavily parasitized by Shiny Cowbirds (Molothrus bonariensis). We found that 56 of 94 Creamy-bellied Thrush nests (60%) found during nest building or egg laying were parasitized by Shiny Cowbirds, and the mean number of cowbird eggs per parasitized nest was 1.6 ± 0.1 (N = 54 nests). At least one thrush egg was punctured in 71% (40/56) of parasitized nests, and 42% (16/38) of nonparasitized nests. We found that cowbird hatching success did not differ among nests where zero, one, or two thrush eggs were punctured and that the proportion of egg punctures associated with parasitism decreased as incubation progressed. Thus, our results do not support the incubation-efficiency, nest-predation, or test-incubation hypotheses. However, the survival of cowbird chicks in our study was negatively associated with the number of thrush chicks. Thus, our results support the competition-reduction hypothesis, with Shiny Cowbirds reducing competition between their young and host chicks by puncturing host eggs in parasitized nests. © 2009 Association of Field Ornithologists.
format JOUR
author Astie, A.A.
Reboreda, J.C.
author_facet Astie, A.A.
Reboreda, J.C.
author_sort Astie, A.A.
title Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests
title_short Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests
title_full Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests
title_fullStr Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests
title_full_unstemmed Function of egg punctures by Shiny Cowbirds in parasitized and nonparasitized Creamy-bellied Thrush nests
title_sort function of egg punctures by shiny cowbirds in parasitized and nonparasitized creamy-bellied thrush nests
url http://hdl.handle.net/20.500.12110/paper_02738570_v80_n4_p336_Astie
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AT reboredajc functionofeggpuncturesbyshinycowbirdsinparasitizedandnonparasitizedcreamybelliedthrushnests
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