Shiny cowbirds share nests, but not mothers, in multiply parasitized mockingbird broods

GLOAG, R.; FIORINI, V.D.; REBOREDA, J.C.; KACELNIK, A.

BEHAVIORAL ECOLOGY AND SOCIOBIOLOGY

SPRINGER

Lugar: Berlin; Año: 2014 vol. 68 p. 681 - 689

0340-5443

Obligate brood parasitic birds, such as cowbirds, evade parental care duties by laying their eggs in the nests of other species. Cowbirds are assumed to avoid laying repeatedly in the same nest so as to prevent intrabrood competition between their offspring. However, because searching for host nests requires time and energy, laying more than one egg per nest might be favoured where hosts are large and can readily rear multiple parasites per brood. Such ?repeat parasitism? by females would have important consequences for parasite evolution because young parasites would then incur indirect fitness costs from behaving selfishly. We investigated shiny cowbird (Molothrus bonariensis) parasitism of a large host, the chalk-browed mockingbird (Mimus saturninus), in a population where over 70 % of the parasitized mockingbird nests receive multiple cowbird eggs. We assessed egg maternity directly, using cameras at nests to film the laying of individually-marked females. We also supplemented video data with evidence from egg morphology, after confirming that each female lays eggs of a consistent appearance. From 133 eggs laid, we found that less than 5%were followed by the same female visiting the nest to lay again or to puncture eggs.