Prevalence and Intensity of Parasitic Insects on Puerto Rican Birds

Birds are host to four orders of parasitic insects: flies (Diptera), lice (Psocodea: Phthiraptera), true bugs (Hemiptera), and fleas (Siphonaptera). These parasites can lower host fitness and thus require birds to invest in defenses to minimize fitness losses. In Puerto Rico, virulent parasites, such as Philornis spp. flies, threaten endangered species and subspecies of birds. Philornis larvae are hematophagous and burrow beneath the skin of both nestling and adult birds. Unfortunately, little is known regarding the prevalence and intensity of subcutaneous Philornis flies of adult birds in Puerto Rico. Here, we inspected 430 birds, representing 38 species, for Philornis infestation. We found Philornis larvae on only four birds, despite previous studies reporting high Philornis prevalence on adults of a single Puerto Rican species, Pearly-eyed Thrashers (Margarops fuscatus). Our results are consistent with other studies suggesting that the prevalence and intensity of Philornis is low in most adult and fledgling birds, compared to nestlings. Our data suggest that Philornis infestation is not a major threat to adult birds in Puerto Rico. In contrast, we show that parasitic lice are relatively common on Puerto Rican birds. Of 309 birds dusted for ectoparasites, 163 (53%) were infested with lice. None of the 309 birds were infested with parasitic fleas or bugs. Our results confirm other recent work showing relatively high prevalence and intensity of lice on birds in humid regions of the world.