Louse Flies of Charadrii and Scolopaci Shorebirds Migrating through Central Europe.

Louse flies are blood-sucking ectoparasites of birds and mammals of veterinary and medical importance. These flies damage host skin and serve as vectors for blood-associated pathogens. Little is known about their phenology, host selection, and prevalence in wild birds. Our study provided a broad-scale assessment of louse flies parasitizing Charadrii and Scolopaci shorebirds during their migration through Central Europe. We collected louse flies from 3,129 specimens in 22 species of shorebirds at a major migratory stopover site in central Poland in 2011-17. In total, 31 Ornithomya avicularia and 15 Ornithomya chloropus specimens occurred on five wader species: Common Snipe (Gallinago gallinago), Ruff (Calidris pugnax), Dunlin (Calidris alpina), Curlew Sandpiper (Calidris ferruginea), and Wood Sandpiper (Tringa glareola). Prevalences ranged from 0.23% to 4.62%. No individual birds were infested by both species of fly, and no flies were found on an additional 17 wader species. The rarer of the two flies, O. chloropus, occurred on all infested bird species, whereas O. avicularia occurred only on Common Snipe and Curlew Sandpiper. In comparison with the other four infested wader species, Common Snipe (n=1,194) was more frequently infested with O. avicularia than with O. chloropus. Our study shows that the prevalence of louse flies on shorebirds is much lower than on other avian taxa. Ecologic and evolutionary mechanisms leading to the relative rarity of louse flies on shorebirds remain to be understood.