all of which are obligate parasites of nestling birds. Philornis species are native to the
Neotropics and widely distributed from Florida to Argentina. Most research on this group has
focused on P. downsi, which was introduced to the Galápagos Islands in the late twentieth
century. Although Philornis parasitism kills nestlings in several native host species, nowhere
do the effects seem more severe than in P. downsi in the Galápagos. Here, we review …