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Data and code from: Forest bird body condition and fruit consumption related to Spotted wing Drosophila abundance and fruit parasitism

Roche, Daniel1; Stoleson, Scott2; Rota, Christopher1; Oldland, William2; Lituma, Christopher1

Research facility: US Forest Service
Published Jun 09, 2026 on Dryad. https://doi.org/10.5061/dryad.zw3r228nw

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Abstract

Migratory bird species are under heavy energetic demands following the breeding season. Birds must first complete a pre-migratory molt and build fat deposits during the post-breeding season for migration. Many birds utilize early successional habitat, consuming fruit resources for energy, and using cover provided by vegetation. Spotted wing Drosophila (Drosophila suzukii, SWD) is a frugivorous non-native invasive insect pest in the United States that parasitizes the ripening fruits of many wild fruiting plants which could affect birds reliant on fruits during a critical time of year. We evaluated what factors, especially those related to SWD abundance and parasitism, related to body condition of several bird species and probability of consumption of fruits by frugivorous birds in regenerating harvests invaded by SWD during the post-breeding season and fall migration. We used mist nets to catch birds in regenerating harvests at Allegheny National Forest from July to October in 2019 and 2020 and measured multiple indices of body condition (subcutaneous fat, molt progression, and scaled mass index [SMI]) for several species. We also collected fecal samples from several frugivorous species for evidence of fruit consumption. We assessed fruit resources and vegetation structure at each mist net using transect surveys. We trapped SWD at each mist net for the duration of mist netting sessions and collected fruit samples to determine the extent of fruit parasitism by SWD at each mist net. Multiple condition indices for several species were correlated with relative abundance of SWD and parasitism of fruits, though the directions of relationships varied and were species-specific. Probability of Allegheny blackberry (Rubus allegheniensis) fruit consumption by frugivorous birds was positively correlated with parasitism of fruits at both the guild and species level. Most species improved condition indices as the season progressed, likely due to dietary flexibility. Future research should include how bird condition changes in relation to foraging microhabitat selection and SWD, selection or rejection of SWD-parasitized fruits by frugivores, use of nutritional metrics to assess quality of SWD and SWD-parasitized fruits, arthropod community responses to SWD, and the possible long-term consequences of changes to fruit consumption and seed dispersal.