Co-parasitism in the face of predation: Effects of natural enemies on a neotropical mockingbird

Co-parasitism is ubiquitous and has important consequences for the ecology and evolution of wild host populations. Studies of parasite co-infections remain limited in scope, with few experimental tests of the fitness consequences of multiple parasites, especially in natural populations.
We measured the separate and combined effects of Philornis seguyi nest flies and shiny cowbirds (Molothrus bonariensis) on the fitness of a shared host, the chalk-browed mockingbird (Mimus saturninus) in Argentina.
Using a two-factor experimental approach, we manipulated the presence of nest flies and cowbirds in mockingbird nests and assessed their effects on mockingbird hemoglobin levels, begging and provisioning rates, body size, and fledging success. We also monitored rates of nest predation in relation to parasitism by flies and cowbirds.
Nest flies reduced the hemoglobin concentration, body size, and fledging success of mockingbirds, likely because mockingbirds did not compensate for parasitism by ..., ,