Disentangling direct and indirect effects of local temperature on abundance of mountain birds and implications for understanding global change impacts

Sensitivity of tropical montane birds to anthropogenic disturbance and management strategies for their conservation in agricultural landscapes

Tropical montane bird communities are hypothesized to be highly sensitive to anthropogenic disturbance because species are adapted to a narrow range of environmental conditions and display high rates of endemism. We assessed avian sensitivity at regional and continental scales for a global epicenter of montane bird biodiversity, the tropical Andes. Using data from an intensive field study of cloud forest bird communities across 7 landscapes undergoing agricultural conversion in northern Peru (1800-3100 m, 2016-2017) and a pan-Andean synthesis of forest bird sensitivity, we developed management strategies for maintaining avian biodiversity in tropical countrysides and examined how environmental specialization predicts species-specific sensitivity to disturbance. In Peru, bird communities occupying countryside habitats contained 29-93% fewer species compared with those in forests and were compositionally distinct due to high levels of species turnover. Fragments of mature forest acted as reservoirs for forest bird diversity, especially when large or surrounded by mixed successional vegetation. In high-intensity agricultural plots, an addition of 10 silvopasture trees or 10% more fencerows per hectare increased species richness by 18-20%. Insectivores and frugivores were most sensitive to disturbance: abundance of 40-70% of species declined in early successional vegetation and silvopasture. These results were supported by our synthesis of 816 montane bird species studied across the Andes. At least 25% of the species declined due to all forms of disturbance, and the percentage rose to 60% in agricultural landscapes. The most sensitive species were those with narrow elevational ranges and small global range sizes, insectivores and carnivores, and species with specialized trophic niches. We recommend protecting forest fragments, especially large ones, and increasing connectivity through the maintenance of early successional vegetation and silvopastoral trees that increase avian diversity in pastures. We provide lists of species-specific sensitivities to anthropogenic disturbance to inform conservation status assessments of Andean birds.

The foraging ecology of yellow-billed and red- billed choughs changed between two climatically different years

Climate change is affecting the alpine ecosystem at an unprecedented rate, with marked changes in spring phenology and the elevation distribution of birds. Changes in the European Alps are happening rapidly, and it is possible behaviours stand to change from one year to the next. The year 2022 was characterised by climatic extremes: Italy experienced its hottest year ever, and it was the driest since 1800. Here, we assessed whether the foraging ecology of two coexisting upland bird species, the yellow-billed and the red-billed chough, changed from 2021 to 2022. We assessed foraging stay times, flock size, propensity to mixed flocking, foraging home ranges and altitudinal distribution. Stay times of both species when foraging in monospecific flocks significantly shortened in 2022, especially in the case of the red-billed chough. The two corvids are known to influence each other when foraging together. In 2021, as expected, the stay times of the red-billed chough decreased when in the presence of the congener, but this did not occur in 2022. Instead, the yellow-billed chough increased its altitudinal foraging distribution in 2022. The results are in line with the hypothesis that large climate variations may disrupt the foraging ecology of mountain birds. However, as it is not possible to draw solid conclusions from just two years of observations, further field research will have to be planned in the future.

Finding food in a changing world: Small-scale foraging habitat preferences of an insectivorous passerine in the Alps

Organisms living in high-elevation habitats are usually habitat specialists who occupy a narrow ecological niche. To envision the response of alpine species to a changing environment, it is fundamental to understand their habitat preferences on multiple spatial and temporal scales. However, information on small-scale habitat use is still widely lacking. We investigated the foraging habitat preferences of the migratory northern wheatear Oenanthe oenanthe during the entire presence at a breeding site in the central Alps. We repeatedly observed 121 adult and juvenile individuals. We applied Bayesian logistic regression models to investigate which habitat characteristics influenced foraging habitat selection on a fine spatial scale, and how habitat use varied temporally. Throughout their presence on the breeding grounds, northern wheatears showed a consistent preference for a mosaic of stones and bare ground patches with slow-growing, short vegetation. The proximity of marmot burrows was preferred, whereas dense and low woody vegetation was avoided. After arrival at the breeding site, short vegetation, preferably close to the snow, was favored. The preference for open habitat patches that provide access to prey underlines the critical role of small-scale habitat heterogeneity for northern wheatears. The strong and consistent preference for a habitat that is under pressure from land-use and climate change suggests that this alpine bird species may be sensitive to habitat loss, leading to a potential range contraction. We highlight the need to conserve habitat diversity on a small spatial scale to ensure the long-term availability of suitable habitat for northern wheatears in the Alps.

Identifying climate refugia for high-elevation Alpine birds under current climate warming predictions

Identifying climate refugia is key to effective biodiversity conservation under a changing climate, especially for mountain-specialist species adapted to cold conditions and highly threatened by climate warming. We combined species distribution models (SDMs) with climate forecasts to identify climate refugia for high-elevation bird species (Lagopus muta, Anthus spinoletta, Prunella collaris, Montifringilla nivalis) in the European Alps, where the ecological effects of climate changes are particularly evident and predicted to intensify. We considered future (2041-2070) conditions (SSP585 scenario, four climate models) and identified three types of refugia: (1) in-situ refugia potentially suitable under both current and future climate conditions, ex-situ refugia suitable (2) only in the future according to all future conditions, or (3) under at least three out of four future conditions. SDMs were based on a very large, high-resolution occurrence dataset (2901-12,601 independent records for each species) collected by citizen scientists. SDMs were fitted using different algorithms, balancing statistical accuracy, ecological realism and predictive/extrapolation ability. We selected the most reliable ones based on consistency between training and testing data and extrapolation over distant areas. Future predictions revealed that all species (with the partial exception of A. spinoletta) will undergo a range contraction towards higher elevations, losing 17%-59% of their current range (larger losses in L. muta). We identified ~15,000 km² of the Alpine region as in-situ refugia for at least three species, of which 44% are currently designated as protected areas (PAs; 18%-66% among countries). Our findings highlight the usefulness of spatially accurate data collected by citizen scientists, and the importance of model testing by extrapolating over independent areas. Climate refugia, which are only partly included within the current PAs system, should be priority sites for the conservation of Alpine high-elevation species and habitats, where habitat degradation/alteration by human activities should be prevented to ensure future suitability for alpine species.

The contribution of landscape features, climate and topography in shaping taxonomical and functional diversity of avian communities in a heterogeneous Alpine region

Understanding the effects of landscape composition and configuration, climate, and topography on bird diversity is necessary to identify distribution drivers, potential impacts of land use changes, and future conservation strategies. We surveyed bird communities in a study area located in the Central Alps (Autonomous Province of South Tyrol, northeast Italy), by means of point counts and investigated taxonomic and functional diversity at two spatial scales along gradients of land use/land cover (LULC) intensity and elevation. We also explored how environmental variables influence bird traits and red-list categories. Models combining drivers of different types were highly supported, pointing towards synergetic effects of different types of environmental variables on bird communities. The model containing only LULC compositional variables was the most supported one among the single-group models: LULC composition plays a crucial role in shaping local biodiversity and hence bird communities, even across broad landscape gradients. Particularly relevant were wetlands, open habitats, agricultural mosaics made up of small habitat patches and settlements, ecotonal and structural elements in agricultural settings, and continuous forests. To conserve bird diversity in the Alps, planning and management practices promoting and maintaining small fields, structural elements, and a mosaic of different LULC types should be supported, while preserving continuous forests at the same time. Additionally, pastures, extensively used meadows, and wetlands are key to conservation. These strategies might mitigate the impacts of global change on bird diversity in the Alps and in other European mountain areas.