First Record of Philornis Parasitism of the Snail Kite (Rostrhamus sociabilis)

We investigated parasitism of the Snail Kite (Rostrhamus sociabilis) by diptera in the genus Philornis through analysis of post-fledging nests in rice fields and flooded areas of western Ecuador in 2020 and 2021. Morphological and molecular data led to the identification of two species of Philornis flies (Diptera: Muscidae) within the nest material: P. falsificus and P. downsi. These results represent the first records of Snail Kites as a host species of any species of Philornis. The prevalence of Philornis puparia in Snail Kite nests was 22% in 2020 and 9.7% in 2021. Seventy-four percent of nest attempts successfully fledged at least one young, with the remaining 26% of attempts either failing during incubation or the nestling phase. Nestling mortality attributable to Philornis parasitism appeared to be low. We also documented parasitism of P. falsificus by the parasitoid wasp Spalangia sp. (Hymenoptera; Pteromalidae).