IEGEBA   24053
INSTITUTO DE ECOLOGIA, GENETICA Y EVOLUCION DE BUENOS AIRES
Unidad Ejecutora - UE
artículos
Título:
Strategic egg destruction by brood parasitic cowbirds?
Autor/es:
FIORINI VD; GLOAG R; KACELNIK A; REBOREDA JC
Revista:
ANIMAL BEHAVIOUR
Editorial:
ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD
Referencias:
Lugar: Amsterdam; Año: 2014 vol. 93 p. 229 - 235
ISSN:
0003-3472
Resumen:
Obligate avian brood parasites do not provide direct care to their young but can indirectly increase
their offspring´s success in host nests. One way in which parasitic cowbirds (Molothrus sp.) could
achieve this is through egg-puncturing whereby, prior to laying in a nest, females puncture holes in the
eggs already present so as to reduce the competition that their offspring will later face for food. In this
study we investigated whether cowbirds strategically increase their puncturing effort with increasing
competitiveness of the future brood. We filmed egg-puncturing behaviour by shiny cowbirds (M.
bonariensis) at nests of chalk-browed mockingbirds (Mimus saturninus), a large host whose nests
often receive multiple cowbird eggs. We presented cowbirds with large (4-eggs) or small (1-egg)
clutches of either mockingbird or cowbird eggs, where large clutch sizes predict greater intrabrood
competition than small clutch sizes, and mockingbird eggs (which are larger) predict greater
competition than other cowbird eggs. The number of pecks made per visit by cowbirds and the number
of eggs they successfully punctured was higher in larger clutches, while mockingbird eggs were broken
more than cowbird eggs, but pecked less per visit. The higher number of pecks aimed at cowbird eggs,
despite these producing less-competitive nestmates, could reflect responses to eggshell strength rather
than egg size, as cowbird eggs are harder to break because of their thicker shells and so require more
effort to puncture. Our results show that cowbird puncturing behaviour is not rigid and varies with
nest contents. We suggest this variation is consistent with females increasing their offspring´s chance
of survival.