Mountain ecosystems are under strong environmental pressure and are considered highly vulnerable to climate change, which is likely to lead to forest expansion and loss of open alpine grasslands, threatening many specialized species. However, for most alpine birds, even basic ecological knowledge, such as their diet, remains limited, restricting our capacity to predict how they will respond to environmental change in the future. In this study, we investigated the diet of the Northern Wheatear Oenanthe oenanthe, a characteristic species of alpine grasslands, in the Italian Alps. We analysed 151 faecal samples collected in 2023 and 2024 using DNA metabarcoding, mainly, but not exclusively, from nestlings. At the same time, we quantified arthropod availability (measured by abundance and biomass) across the breeding season using sweep nets and pitfall traps. The Northern Wheatear's diet consisted of a broad range of arthropods, mainly Diptera, Coleoptera, Lepidoptera and Orthoptera. For most arthropod groups, there was not one peak in availability across the breeding season, but a continuum moving upwards as the season progressed. A compositional selectivity analysis showed that Northern Wheatears exhibited a generalist foraging strategy at the Order level, with no overall preference for specific taxa, although selectivity for Lepidoptera and Orthoptera showed seasonal variation. This suggests that, in the face of global changes, Northern Wheatears can adjust their foraging to temporal and spatial variation in arthropod community composition, provided that overall prey availability remains sufficient. We found no relationship between breeding performance and arthropod availability. Given that nestling starvation has never been recorded in this population, it is likely that the spatio-temporal dynamism of alpine habitats maintains high food availability throughout the season, preventing food limitation during breeding.
Dietary flexibility and high arthropod availability prevent food limitation in a mountain population of breeding Northern Wheatears
Mermillon, Camille
;Chamberlain, Dan;
2026-01-01
Abstract
Mountain ecosystems are under strong environmental pressure and are considered highly vulnerable to climate change, which is likely to lead to forest expansion and loss of open alpine grasslands, threatening many specialized species. However, for most alpine birds, even basic ecological knowledge, such as their diet, remains limited, restricting our capacity to predict how they will respond to environmental change in the future. In this study, we investigated the diet of the Northern Wheatear Oenanthe oenanthe, a characteristic species of alpine grasslands, in the Italian Alps. We analysed 151 faecal samples collected in 2023 and 2024 using DNA metabarcoding, mainly, but not exclusively, from nestlings. At the same time, we quantified arthropod availability (measured by abundance and biomass) across the breeding season using sweep nets and pitfall traps. The Northern Wheatear's diet consisted of a broad range of arthropods, mainly Diptera, Coleoptera, Lepidoptera and Orthoptera. For most arthropod groups, there was not one peak in availability across the breeding season, but a continuum moving upwards as the season progressed. A compositional selectivity analysis showed that Northern Wheatears exhibited a generalist foraging strategy at the Order level, with no overall preference for specific taxa, although selectivity for Lepidoptera and Orthoptera showed seasonal variation. This suggests that, in the face of global changes, Northern Wheatears can adjust their foraging to temporal and spatial variation in arthropod community composition, provided that overall prey availability remains sufficient. We found no relationship between breeding performance and arthropod availability. Given that nestling starvation has never been recorded in this population, it is likely that the spatio-temporal dynamism of alpine habitats maintains high food availability throughout the season, preventing food limitation during breeding.
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