Burrowing fly larvae (Philornis porteri) associated with mortality of eastern bluebirds in Florida

We investigated mortality among nestling eastern bluebirds (Sialia sialis) in Polk and Highlands counties, Florida (USA) in 1999-2001. At least six species of maggots from three families of muscoid flies, Calliphoridae, Sarcophagidae, and Muscidae were found associated with the nestlings. Philornis porteri, the only species of obligate bird parasite collected, was found in the contents of two nests, in the ear canal and the musculature of the jaw of one nestling, and in the abdominal subcutis of another. This is the first record of bluebird parasitism by P. porteri. Although some nestlings were infested by tissue-invading fly larvae antemortem, the role of these maggots in the overall mortality was not clear.