IEGEBA   24053
INSTITUTO DE ECOLOGIA, GENETICA Y EVOLUCION DE BUENOS AIRES
Unidad Ejecutora - UE
artículos
Título:
PREFORMATIVE MOLT IN BROOD PARASITIC SCREAMING (MOLOTHRUS RUFOAXILLARIS) AND SHINY (M. BONARIENSIS) COWBIRDS
Autor/es:
URSINO, CYNTHIA; FACCHINETTI, CAROLINA; REBOREDA, JUAN CARLOS
Revista:
ORNITOLOGIA NEOTROPICAL
Editorial:
NEOTROPICAL ORNITHOLOGICAL SOC
Referencias:
Lugar: ALEMANIA; Año: 2012 vol. 23 p. 163 - 171
ISSN:
1075-4377
Resumen:
Molt and plumage cycles are poorly known in Neotropical birds in general and in South American
brood parasitic cowbirds in particular. The Screaming Cowbird (Molothrus rufoaxillaris) is one of the more
specialized brood parasites that use almost exclusively the Baywing (Agelaioides badius), while the Shiny
Cowbird (M. bonariensis) is an extreme generalist brood parasite that uses more than 250 known hosts.
Fledglings of Screaming Cowbird are mimetic in plumage coloration to fledglings of Baywings, while Shiny
Cowbird fledglings have female-like plumage. We measured and analyzed plumage changes of Screaming
and Shiny Cowbirds since the time of fledging (i.e. 12-14 days of age) until young completed the preformative
molt. There were not sexual differences in molting pattern for both species. Screaming Cowbirds started to
molt before Shiny Cowbirds (37 vs. 61 days of age). They first molted under-wing coverts, followed by chest,
the rest of the body, and finally tail and external coverts. Shiny cowbird molt started at the crown, breast and
back, followed by throat, under-wing coverts, and finally upper-wing covers and tail. In both species flight
feathers began molting after body feathers and the pattern of molt was similar, starting with the primaries.
For both species the preformative molt was completed at the same age (167-181 days). The beginning of the
preformative molt in Screaming Cowbirds coincides with the age at which young become independent of their
foster parents and join conspecific flocks. This shorter latency to