Behavioral plasticity of Shiny Cowbirds when they parasitize hosts of different size

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

Melbourne, Florida

Congreso; 18th Annual International Conference on Comparative Cognition; 2011

The Shiny Cowbird, Molothrus bonariensis, is an extreme generalist brood parasite that uses more than 200 hosts that differ greatly in body size (range 10-80 g.). Female cowbirds (body mass 40-45 g) synchronize parasitism with host laying and peck and puncture host eggs when visit host nests. This virulent behavior may be adaptive when they parasitize large hosts, as they remove stronger competitors. However, cowbird chicks may also benefit from sharing the nest with smaller host chicks because begging by host chicks solicits a higher provisioning rate by the parents that could be monopolized by the parasite. We studied the plasticity of shiny cowbird parasitic behavior in two hosts that differ greatly in body mass (13 vs. 75 g). Cowbird females laid larger eggs, improved synchronization between parasitism and host laying and punctured more host eggs per parasitic event when they parasitized the large host. In addition, cowbird chicks raised in nests of the large host had higher begging intensity, longer begging bouts, spent more time begging and had shorter latency to beg than those raised in nests of the small host. These differences between hosts indicate that shiny cowbirds may adaptively adjust parasitic behaviors to host characteristics.