Dr Sabine Tebbich (University of Vienna), Behavioural changes in an invasive parasitic fly and its avian hosts, the Darwin’s finches

The parasitic fly Philornis downsi, is an obligate parasite of bird nestlings. The larvae live in the nests and sucks blood from the nestlings. This recently introduced parasite has a dramatic impact on the bird community of Galápagos. Previous studies did show that the Darwin’s finches suffer a high brood loss due to parasitism and this contributes to the dramatic decline of several species. Our data suggest that behavioural changes have evolved in both the host and the parasite in this recently established host parasite interaction. The parasite has changed its oviposition behaviour: while previously it laid its eggs only in nests where chicks had already hatched, it now already lays in incubating nests. At least one host species seems to react by abandoning the parasitized nests during the incubating stage and several host species have shown a new form of tool use. They take leaves of an endemic plant species with repellent properties and rub them into their feathers.