Shiny Cowbirds benefits of puncturing host eggs and synchronizing parasitism in hosts smaller and larger than the parasite

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

Veracruz, México

Congreso; 4th. North American Ornithological Conference; 2006

Ornithological Societies of North America

Shiny Cowbirds usually synchronize parasitism with host laying and puncture host eggs. Synchronization of parasitism may enhance the chances of survival of parasite chicks. Similarly, puncture of host eggs may enhance the efficiency of incubation of parasite eggs and/or reduce the competition for food between parasite and host chicks. The benefits of synchronizing parasitism and puncturing host eggs may depend of host body size. We analyzed the effects of synchronization of parasitism and egg puncturing in hosts smaller (House Wren) and larger (Chalk-browed Mockingbird) than the parasite. We parasitized host´s with natural cowbird eggs and measured hatchability and chick survival in four experimental groups: parasitism synchronized with host laying and low or high number of host eggs, and parasitism not synchronized and low or high number of eggs. Lack of synchronization reduced chick survival in the larger but not in the smaller host. Number of host eggs did not affect the efficiency of incubation in either hosts, but it affected chick survival in the larger host. Correlational data showed that the proportion of parasite´s eggs synchronized and host´s eggs punctured was higher in the larger host, suggesting that Shiny Cowbirds may adjust these behaviors to host characteristics.