Shiny cowbird have louder and longer begging calls in large than in small hosts

TUERO, D.T.; REBOREDA, J.C.

Perth

Congreso; 13th International Society of Behavioral Ecology Congress; 2010

We studied if the size of the host affects the begging behaviour of shiny cowbird (Molothrus bonariensis) chicks. We experimentally parasitized nests of two hosts, the chalk-browed mockingbird (Mimus saturninus, 75 g) and the house wren (Troglodytes aedon, 13 g). Because cowbird females that use mockingbirds and wrens differ genetically, to separate genetic and environmental factors we also parasitized wren nests with cowbird eggs laid in mockingbird nests. In both hosts we controlled for number of host chicks and cowbird short-term need. We analyzed begging behaviour and food obtained by cowbird chicks when they were 4 days of age. The amount of food obtained by cowbirds was higher in mockingbird than in wren nests. There were no differences in begging behaviour of cowbird chicks raised in wren nests regardless of the origin of the eggs. However, cowbird chicks raised in mockingbird nests had higher begging intensity, longer begging bouts, spent more time begging and had shorter latency to beg than those raised in wren nests. Our results show that the size of host chicks which shiny cowbird chicks are raised with affects the begging behaviour of the parasite.