Abstract

MEZQUIDA, Eduardo T. Botfly parasitism in passerine birds in the central Argentine monte during wet and dry years. Hornero [online]. 2020, vol.35, n.1, pp.20-28. ISSN 0073-3407.

Avian parasites may exert an important selective pressure on host populations, although their impact may vary depending on environmental conditions. The Neotropical flies of the genus Philornis include species whose larvae parasitize the nestlings of several bird species. Here, I analyze the prevalence of parasitic flies in passerine species nesting in a semiarid area in the central Monte of Argentina, during four breeding seasons with contrasting weather conditions. Specifically, I quantify the prevalence in different avian hosts, its inter-annual and seasonal variation, the influence of precipitation and host availability, and the effect of parasitism on nestling mortality. Botfly parasitism was observed in 8 of the 21 passerine species for which nestling development could be followed. Prevalence for parasitized species was, on average, 15%, mainly affecting species in Thraupidae (21%), Mimidae (14%), and Tyrannidae (7%). Botfly parasitism occurred at the end of the breeding season in two of the four years studied, coinciding with increased late spring precipitations. Environmental conditions also favored greater host availability. Nestling mortality due to botfly parasitism was found in 10% of parasitized nests. Results indicate that the prevalence of botfly parasitism is relatively low in the central Monte, and it is positively related to wet conditions during late spring, mainly affecting avian species that breed later in the season. However, future global change scenarios could increase the negative effect of this parasite, particularly in host species of conservation concern.

Keywords : Monte biome; Climatic conditions; Philornis; Parasite prevalence; Host use.

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