Brown-and-yellow Marshbird (Pseudoleistes virescens) as a host of the Screaming Cowbird (Molothrus rufoaxillaris): first evidence of fledglings’ attendance

Myriam E. Mermoz; Emilio M. Charnelli

doi:10.56178/eh.v40i2.1523

Artículos Publicado 29 noviembre 2025 https://doi.org/10.56178/eh.v40i2.1523

El Pecho Amarillo (Pseudoleistes virescens) como hospedador del Tordo Pico Corto (Molothrus rufoaxillaris): primera evidencia de cuidado de sus volantones

calidad del hospedador cría cooperativa cuidado parental hospedador efectivo parásito de cría selección de hospedadores

Myriam E. Mermoz Instituto de Ecología, Genética y Evolución de Buenos Aires (IEGEBA-UBA-CONICET), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Argentina

Emilio M. Charnelli Sarmiento 1176, General Madariaga, Argentina

Resumen

El Tordo Pico Corto (Molothrus rufoaxillaris) es un parásito de cría altamente especializado que principalmente parasita al Músico (Agelaioides badius). Siendo parasitado con una frecuencia marcadamente menor, el Pecho Amarillo (Pseudoleistes virescens) ha sido reportado como ‘hospedador alternativo’. Sin embargo, los estudios previos finalizaron cuando los volantones de Tordo Pico Corto abandonaron el nido. En 2024, durante un estudio sobre el éxito reproductivo y supervivencia de los volantones de Pecho Amarillo en General Madariaga (provincia de Buenos Aires, Argentina), detectamos que 15.6% de los nidos (n = 10) fueron parasitados por Tordo Pico Cortos. Cuatro de esos nidos alcanzaron el estadio de volantón. Registramos el cuidado parental fuera del nido de dos volantones de Tordo Pico Corto de un nido hasta 20 días luego de abandonarlo. Dado que los pichones de Tordo Pico Corto permanecen en el nido hasta los 7-12 días de edad, el tiempo total de cuidado parental por parte de los Pecho Amarillo hacia esos pichones fue de 32 días. Este valor está incluido dentro del rango de 30-40 días reportado en Músico. La calidad reportada (pichones aptos para volar) de los hospedadores alternativos, incluyendo al Pecho Amarillo, es similar a la del Músico. Entonces, la alta preferencia de los Tordo Pico Corto por el Músico podría estar relacionada con la competencia interespecífica con el altamente generalista Toro Renegrido (Molothrus bonariensis) en la mayor parte de sus hospedadores potenciales.

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Referencias

Antonson ND, Rubenstein DR, Hauber ME, Botero CA (2020) Ecological uncertainty favours the diversification of host use in avian brood parasites. Nature Communications 11(1):4185. https://doi.org/10.1038/s41467-020-18038-y
Barros R (2015) El Mirlo de pico corto Molothrus rufoaxillaris, una nueva especie para Chile. La Chiricoca 19:36-44. http://www.lachiricoca.cl/wp-content/uploads/2018/03/La-Chiricoca-19_part5_c.pdf
Chaneton EJ, Perelman SB, León RJC (2005) Floristic heterogeneity of Flooding Pampa grasslands: a multi-scale analysis. Plant Biosystems 139(3):245-254. https://doi.org/10.1080/11263500500340714
De Mársico MC, Reboreda JC (2008) Differential reproductive success favours strong host preference in a highly specialized brood parasite. Proceedings of the Royal Society of London B 275(1650):2499-2506. https://doi.org/10.1098/rspb.2008.0700
De Mársico MC, Mahler B, Chomnalez M, Di Giácomo AG, Reboreda JC (2010) Host use by generalist and specialist brood-parasitic cowbirds at population and individual levels. In: Macedo R (ed). Advances in the Study of Behavior (Vol 42), Academic Press, Burlington. Pp 83-121. https://doi.org/10.1016/S0065-3454(10)42003-3
Di Giacomo AG, Reboreda JC (2015) Reproductive success of the specialist brood parasite Screaming Cowbird in an alternative host, the Chopi Blackbird. The Auk 132(1):16-24. https://doi.org/10.1642/AUK-13-008.1
Fraga RM (1979) Differences between nestlings and fledglings of Screaming and Bay-winged Cowbirds. The Wilson Bulletin 91(1):151-154
Fraga RM (1991) The social system of a communal breeder, the Bay-winged Cowbird Molothrus badius. Ethology 89(3):195-210. https://doi.org/10.1111/j.1439-0310.1991.tb00304.x
Fraga RM (1996) Further evidence of parasitism of Chopi Blackbirds (Gnorimopsar chopi) by the specialized Screaming Cowbird (Molothrus rufoaxillaris). The Condor 98(4):866-867. https://doi.org/10.2307/1369874
Fraga RM (1998) Interactions of the parasitic Screaming and Shiny Cowbirds (Molothrus rufoaxillaris and M. bonariensis) with a shared host, the Bay-winged Cowbird (M. badius). In: Rothstein, SI Robinson SK (eds) Parasitic birds and their hosts, studies in coevolution, Oxford University Press, New York pp 173-193
Fraga RM (2008) Notes on the nesting of Chopi Blackbirds (Gnorimopsar chopi) in Argentina and Paraguay, with data on cooperative breeding and brood parasitism by Screaming Cowbirds (Molothrus rufoaxillaris). Ornitología Neotropical 19:299-303
Hudson WH (1874) Notes on the procreant instincts of the three species of Molothrus found in Buenos Ayres. Proceedings of the Zoological Society of London 42(1):153-174. https://doi.org/10.1111/j.1096-3642.1874.tb02466.x
Hudson WH (1920) Birds of La Plata. Dent and Sons Ltd, Toronto, Canada
Jaramillo A, Burke P (1999) New World blackbirds: the Icterids. Princeton University Press, Princeton, New Jersey
Lima RD (2021) An obligate brood parasite, the Screaming Cowbird (Molothrus rufoaxillaris), more than doubled its range expanding northeastward in the last decades. Ornithology Research 29(2): 63-67. https://doi.org/10.1007/s43388-021-00052-3
López-Lanús B (2008) Bird sounds from southern South America (DVD). Audiornis Producciones, Buenos Aires
Lowther PE (2025) Lists of victims and hosts of the parasitic cowbirds (Molothrus). [URL: https://www.datocms-assets.com/44232/1747156260-host-list-molothrus-ver09may2025.pdf]
Mermoz ME, Reboreda JC (1996) New host for a specialized brood parasite, the screaming cowbird. The Condor 98: 630-632
Mermoz ME, Fernández GJ (2003) Breeding success of a specialist brood parasite, the Screaming Cowbird, parasitizing an alternative host. The Condor 105(1):63-72. https://doi.org/10.1093/condor/105.1.63
Mermoz ME, Reboreda JC (2003) Reproductive success of Shiny Cowbird (Molothrus bonariensis) parasitizing the larger Brown-and-yellow Marshbird (Pseudoleistes virescens) in Argentina. The Auk 120(4):1128-1139. https://doi.org/10.1093/auk/120.4.1128
Mermoz ME, Depalma DM, Charnelli EM, Zilli C (2021a) First record of parasitism of Scarlet-headed Blackbird (Amblyramphus holosericeus) by the specialized Screaming Cowbird (Molothrus rufoaxillaris). El Hornero 36(1):91-100. https://doi.org/10.56178/eh.v36i1.434
Mermoz ME, Villarruel C, de la Colina A, Mahler B (2021b) Fledgling sex-ratio is biased towards the helping sex in a Neotropical cooperative breeder, the brown-and-yellow marshbird (Pseudoleistes virescens). Behaviour. 158(2):135-160. https://doi.org/10.1163/1568539X-bja10061
Mermoz ME, Svagelj WS, Fernández GJ (2025) Helpers-at-the nest mitigate the costs of cowbird brood parasitism in brown-and-yellow marshbirds. Ornithology Research 33(1):11. https://doi.org/10.1007/s43388-024-00218-9
Molina-Morales M, Martínez JG, Avilés JM (2016) Criteria for host selection in a brood parasite vary depending on parasitism rate. Behavioural Ecology 27(5):1441–1448. https://doi.org/10.1093/beheco/arw066
Orians GH, Orians CE, Orians KJ (1977) Helpers at the nest in some Argentine blackbirds. In: Stonehouse B Perrins C. (eds) Evolutionary Ecology. Palgrave, London. https://doi.org/10.1007/978-1-349-05226-4_13
Orians GH (1980) Some adaptations of marsh-nesting blackbirds. Vol.14 Princeton University Press, Princeton
Pantoja V, Medrano F, Tejeda I (2023) Range expansion of the Screaming Cowbird (Molothrus rufoaxillaris) mediated by a new brood parasite-host interaction in central Chile. Gayana 87(1):18-24. https://doi.org/10.4067/S0717-65382023000100018
Rothstein SI (1990) A model system for coevolution: avian brood parasitism. Annual Review of Ecology and Systematics 21:481-508
Reboreda JC, Fiorini VD, De Mársico MC, Gloag R, Scardamaglia RC (2018) Parasitic Behaviour of Interspecific Brood Parasitic Females. In: Soler, M. (eds) Avian Brood Parasitism. Fascinating Life Sciences. Springer, Cham. https://doi.org/10.1007/978-3-319-73138-4_18. Pp 325-342
Sick H (1985) Ornitologia brasileira: uma introducçao. University of Brasilia, Brasilia
Soler M (2018) Brood Parasitism in Birds: A Coevolutionary Point of View. In: Soler, M. (eds) Avian Brood Parasitism. Fascinating Life Sciences. Springer, Cham. https://doi.org/10.1007/978-3-319-73138-4_1. Pp 1-19
Spottiswoode CN, Kilner RM, Davies NB (2012) Brood parasitism. In: Royle NJ, Smiseth PT, Kölliker M (eds) The evolution of parental care. Oxford University Press, Oxford
Ursino CA, Facchinetti C, Reboreda JC (2012) Preformative molt in brood parasitic Screaming (Molothrus rufoaxillaris) and Shiny (M. bonariensis) Cowbirds. Ornitología Neotropical 23:150-168

Cómo citar

Myriam E. Mermoz, Emilio M. Charnelli (2025). El Pecho Amarillo (Pseudoleistes virescens) como hospedador del Tordo Pico Corto (Molothrus rufoaxillaris): primera evidencia de cuidado de sus volantones. El Hornero, Vol. 40 Núm. 2 (2025), 61-67. https://doi.org/10.56178/eh.v40i2.1523

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[1] Antonson ND, Rubenstein DR, Hauber ME, Botero CA (2020) Ecological uncertainty favours the diversification of host use in avian brood parasites. Nature Communications 11(1):4185. https://doi.org/10.1038/s41467-020-18038-y

[2] Barros R (2015) El Mirlo de pico corto Molothrus rufoaxillaris, una nueva especie para Chile. La Chiricoca 19:36-44. http://www.lachiricoca.cl/wp-content/uploads/2018/03/La-Chiricoca-19_part5_c.pdf

[3] Chaneton EJ, Perelman SB, León RJC (2005) Floristic heterogeneity of Flooding Pampa grasslands: a multi-scale analysis. Plant Biosystems 139(3):245-254. https://doi.org/10.1080/11263500500340714

[4] De Mársico MC, Reboreda JC (2008) Differential reproductive success favours strong host preference in a highly specialized brood parasite. Proceedings of the Royal Society of London B 275(1650):2499-2506. https://doi.org/10.1098/rspb.2008.0700

[5] De Mársico MC, Mahler B, Chomnalez M, Di Giácomo AG, Reboreda JC (2010) Host use by generalist and specialist brood-parasitic cowbirds at population and individual levels. In: Macedo R (ed). Advances in the Study of Behavior (Vol 42), Academic Press, Burlington. Pp 83-121. https://doi.org/10.1016/S0065-3454(10)42003-3

[6] Di Giacomo AG, Reboreda JC (2015) Reproductive success of the specialist brood parasite Screaming Cowbird in an alternative host, the Chopi Blackbird. The Auk 132(1):16-24. https://doi.org/10.1642/AUK-13-008.1

[7] Fraga RM (1979) Differences between nestlings and fledglings of Screaming and Bay-winged Cowbirds. The Wilson Bulletin 91(1):151-154

[8] Fraga RM (1991) The social system of a communal breeder, the Bay-winged Cowbird Molothrus badius. Ethology 89(3):195-210. https://doi.org/10.1111/j.1439-0310.1991.tb00304.x

[9] Fraga RM (1996) Further evidence of parasitism of Chopi Blackbirds (Gnorimopsar chopi) by the specialized Screaming Cowbird (Molothrus rufoaxillaris). The Condor 98(4):866-867. https://doi.org/10.2307/1369874

[10] Fraga RM (1998) Interactions of the parasitic Screaming and Shiny Cowbirds (Molothrus rufoaxillaris and M. bonariensis) with a shared host, the Bay-winged Cowbird (M. badius). In: Rothstein, SI Robinson SK (eds) Parasitic birds and their hosts, studies in coevolution, Oxford University Press, New York pp 173-193

[11] Fraga RM (2008) Notes on the nesting of Chopi Blackbirds (Gnorimopsar chopi) in Argentina and Paraguay, with data on cooperative breeding and brood parasitism by Screaming Cowbirds (Molothrus rufoaxillaris). Ornitología Neotropical 19:299-303

[12] Hudson WH (1874) Notes on the procreant instincts of the three species of Molothrus found in Buenos Ayres. Proceedings of the Zoological Society of London 42(1):153-174. https://doi.org/10.1111/j.1096-3642.1874.tb02466.x

[13] Hudson WH (1920) Birds of La Plata. Dent and Sons Ltd, Toronto, Canada

[14] Jaramillo A, Burke P (1999) New World blackbirds: the Icterids. Princeton University Press, Princeton, New Jersey

[15] Lima RD (2021) An obligate brood parasite, the Screaming Cowbird (Molothrus rufoaxillaris), more than doubled its range expanding northeastward in the last decades. Ornithology Research 29(2): 63-67. https://doi.org/10.1007/s43388-021-00052-3

[16] López-Lanús B (2008) Bird sounds from southern South America (DVD). Audiornis Producciones, Buenos Aires

[17] Lowther PE (2025) Lists of victims and hosts of the parasitic cowbirds (Molothrus). [URL: https://www.datocms-assets.com/44232/1747156260-host-list-molothrus-ver09may2025.pdf]

[18] Mermoz ME, Reboreda JC (1996) New host for a specialized brood parasite, the screaming cowbird. The Condor 98: 630-632

[19] Mermoz ME, Fernández GJ (2003) Breeding success of a specialist brood parasite, the Screaming Cowbird, parasitizing an alternative host. The Condor 105(1):63-72. https://doi.org/10.1093/condor/105.1.63

[20] Mermoz ME, Reboreda JC (2003) Reproductive success of Shiny Cowbird (Molothrus bonariensis) parasitizing the larger Brown-and-yellow Marshbird (Pseudoleistes virescens) in Argentina. The Auk 120(4):1128-1139. https://doi.org/10.1093/auk/120.4.1128

[21] Mermoz ME, Depalma DM, Charnelli EM, Zilli C (2021a) First record of parasitism of Scarlet-headed Blackbird (Amblyramphus holosericeus) by the specialized Screaming Cowbird (Molothrus rufoaxillaris). El Hornero 36(1):91-100. https://doi.org/10.56178/eh.v36i1.434

[22] Mermoz ME, Villarruel C, de la Colina A, Mahler B (2021b) Fledgling sex-ratio is biased towards the helping sex in a Neotropical cooperative breeder, the brown-and-yellow marshbird (Pseudoleistes virescens). Behaviour. 158(2):135-160. https://doi.org/10.1163/1568539X-bja10061

[23] Mermoz ME, Svagelj WS, Fernández GJ (2025) Helpers-at-the nest mitigate the costs of cowbird brood parasitism in brown-and-yellow marshbirds. Ornithology Research 33(1):11. https://doi.org/10.1007/s43388-024-00218-9

[24] Molina-Morales M, Martínez JG, Avilés JM (2016) Criteria for host selection in a brood parasite vary depending on parasitism rate. Behavioural Ecology 27(5):1441–1448. https://doi.org/10.1093/beheco/arw066

[25] Orians GH, Orians CE, Orians KJ (1977) Helpers at the nest in some Argentine blackbirds. In: Stonehouse B Perrins C. (eds) Evolutionary Ecology. Palgrave, London. https://doi.org/10.1007/978-1-349-05226-4_13

[26] Orians GH (1980) Some adaptations of marsh-nesting blackbirds. Vol.14 Princeton University Press, Princeton

[27] Pantoja V, Medrano F, Tejeda I (2023) Range expansion of the Screaming Cowbird (Molothrus rufoaxillaris) mediated by a new brood parasite-host interaction in central Chile. Gayana 87(1):18-24. https://doi.org/10.4067/S0717-65382023000100018

[28] Rothstein SI (1990) A model system for coevolution: avian brood parasitism. Annual Review of Ecology and Systematics 21:481-508

[29] Reboreda JC, Fiorini VD, De Mársico MC, Gloag R, Scardamaglia RC (2018) Parasitic Behaviour of Interspecific Brood Parasitic Females. In: Soler, M. (eds) Avian Brood Parasitism. Fascinating Life Sciences. Springer, Cham. https://doi.org/10.1007/978-3-319-73138-4_18. Pp 325-342

[30] Sick H (1985) Ornitologia brasileira: uma introducçao. University of Brasilia, Brasilia

[31] Soler M (2018) Brood Parasitism in Birds: A Coevolutionary Point of View. In: Soler, M. (eds) Avian Brood Parasitism. Fascinating Life Sciences. Springer, Cham. https://doi.org/10.1007/978-3-319-73138-4_1. Pp 1-19

[32] Spottiswoode CN, Kilner RM, Davies NB (2012) Brood parasitism. In: Royle NJ, Smiseth PT, Kölliker M (eds) The evolution of parental care. Oxford University Press, Oxford

[33] Ursino CA, Facchinetti C, Reboreda JC (2012) Preformative molt in brood parasitic Screaming (Molothrus rufoaxillaris) and Shiny (M. bonariensis) Cowbirds. Ornitología Neotropical 23:150-168