Host use by Philornis sp. in a passerine community in central Argentina

Resumen

We studied host use by parasitic botflies (Philornis sp.) in a passerine community in central Argentina and
analyzed characteristics of nests and hosts associated with botfly parasitism. We conducted a four-year field study
as well as a bibliographical survey where we determined: presence of botfly parasitism, type of nest, presence of
green material and small sticks in the nest, average height of the nest, date of last nesting attempt during the breeding
season and egg volume (as a surrogate of species body mass). Our field study of 3 birds species showed that botflies
parasitized Troglodytes aedon (25% of nests), but not Sicalis flaveola and Tachycineta leucorroha in spite of nesting in
similar boxes, at the same place and during the same time of the year. However T. aedon built nests using dry material
while S. flaveola and T. leucorroha used green material.The analysis of published data (35 species considered) showed
a negative association between botfly parasitism and presence of green material in the nest, and a positive association
between botfly parasitism and presence of small sticks in the nest and date of the last nesting attempt during the
breeding season. Our results indicate that the materials used to build the nest and the extent of the breeding season are
factors that influence host use by botflies in central Argentina.