Philornis spp. causes significant mortality in Greater Thornbirds nestlings: experimental evidence

MANZOLI, DARÍO EZEQUIEL; BARENGO, EMILCE; ANTONIAZZI, LEANDRO RAÚL; ARRABAL, JUAN PABLO; SARAVIA, MARÍA JOSE; SILVESTRI, LEONARDO; ROHRMANN, DAVID; BELDOMÉNICO, PABLO

Puerto Iguazú

Conferencia; 59th Annual International Conference of the Wildlife Disease Association; 2010

Wildlife Disease Association

The genus Philornis (Diptera: Muscidae) comprise a group of poorly know flies whose larvae parasitize birds nestlings in the Neotropics. A negative impact on brood success has been demonstrated for the semi-haematophagous Philornis downsi in Galapagos, but for the remaining species of the genus, mostly burrowing subcutaneous larvae, there is only documentation of negative associations between parasitism and mortality, lacking experimental evidence that confirms causation. The goal of this experiment was to dissect the specific impact of subcutaneous Philornis larvae on the survival of nestlings of two of their preferred host species, Pitangus sulphuratus and Phacellodomus ruber. To this aim we conducted a field experiment with a matched design, in which, within a brood, one or more nestlings were randomly assigned to a daily larva removal treatment, from hatching to fledging (or death) Their siblings served as matched controls and larva removal was mocked on them. A total of 58 P. sulphuratus (25 treated and 33 controls) and 27 Ph. ruber (12 treated and 15 controls) were enrolled in the study. The data was analyzed with a Generalized Linear Mixer Model. We found that nestlings of Ph. ruber that underwent larva removal had over 5 time the odds of surviving than those of controls. On the other hand, we did not observe an effect of larva removal on P. sulphuratus nestlings. This differential impact between host species highlight the complexity of host-parasite relationships and warrant further on these biological processes.