High Ectoparasite Loads of Tropical Birds: Chewing Lice on Puerto Rican American Kestrels (Falco sparverius caribaearum).

Ectoparasite loads of birds may be governed, in part, by the climatic characteristics of their environment. We surveyed live-trapped American Kestrels (Falco sparverius caribaearum) for lice and other ectoparasites on the humid subtropical island of Puerto Rico during March-May 2024. The main goal was to compare the prevalence and abundance of lice on kestrels in Puerto Rico to recently published data on the lice of kestrels 1000 km away in the Bahamas, and to the lice of kestrels in an arid region of the western US (Utah). A brief general inspection of the plumage of 39 captured birds was followed by careful examination of the underside of wing primary feathers under a dissecting microscope. Two species of lice were collected, Colpocephalum subzerafae and Degeeriella carruthi, neither previously recorded from kestrels in Puerto Rico. The same two species are present on kestrels in the Bahamas. The prevalence and abundance of lice on kestrels in Puerto Rico and the Bahamas were similar, while being much greater than the prevalence and abundance of lice on kestrels in arid Utah, US. We also collected two species of hippoboscid flies (Diptera: Hippoboscidae): Microlynchia pusilla, not previously recorded on the American Kestrel, and Ornithoctona erythrocephala. These flies, as well as the lice, might affect the health of kestrels both directly, e.g., causing anemia by feeding on blood, and indirectly by vectoring endoparasites.