INVESTIGADORES
DE MARSICO Maria Cecilia
congresos y reuniones científicas
Título:
High pre-fledging but low post-fledging success of shiny cowbirds parasitizing bay-winged cowbirds.
Autor/es:
DE MÁRSICO, MARÍA CECILIA; REBOREDA, JUAN CARLOS
Lugar:
Campos do Jordao, SP
Reunión:
Congreso; 25th International Ornithological Congress; 2010
Resumen:
The
shiny cowbird (Molothrus bonariensis)
is one of the most generalist brood parasites at the species level. However,
shiny cowbirds only rarely parasitizes the bay-winged cowbird (Agelaioides badius), a species sympatric
with many of their primary hosts. The low frequency of parasitism in bay-winged
cowbird nests cannot be explained by the presence of effective antiparasitic
defenses because bay-winged cowbirds neither reject parasite eggs nor show
differential aggression toward shiny cowbird females. We tested the hypothesis
that shiny cowbirds do not use bay-winged cowbirds because the parasites reproductive
success is lower than in other frequently parasitized hosts. The study was
conducted in the Province of Buenos Aires, Argentina, between 2003 and 2009. We
artificially parasitized bay-winged cowbird nests with shiny cowbird eggs or
newly hatched chicks and followed their fate throughout the host nesting cycle.
Our results showed that shiny cowbird egg survival, hatching success and chick
survival were similarly high in bay-winged cowbird nests and in two primary
hosts of the same study area, the chalk-browed mockingbird (Mimus saturninus) and the house wren (Troglodytes aedon). Shiny cowbird chicks
in bay-winged cowbird nests grew faster and reached a higher asymptotic weight
than host chicks, and growth parameters where comparable to those observed in
the primary hosts. However, shiny cowbird fledglings did not receive further
parental care from bay-winged cowbirds once they left the nest, indicating that
mimicry between parasite and host young is critical for the parasites
post-fledging survival. Low
post-fledging survival may explain why shiny cowbirds rarely parasitize
bay-winged cowbirds.