Massive snow flows falling down mountain slopes can clear dense forest and make way for shrubs and smaller trees, allowing a greater variety of bird species to live in the affected area
February 14, 2023
Avalanches create attractive habitats for many bird species, resulting in increased bird diversity in mountainous areas where heavy snow flows have plowed down larger trees.
The sudden, massive snow movements regularly clear sections of the dense, high-crowned forest populated primarily by tits, thrushes and woodpeckers, making way for the growth of shrubs and smaller trees that attract whinchats, pipits and buntings. Taken together, these landscape “mosaics” are home to a variety of bird species, although these could change as climate change affects future avalanche activity, says Riccardo Alba of the University of Turin in Italy.
“I didn’t expect to find such a variety,” he says. “It is crucial to further study the interactions between climate change and biodiversity in mountain areas to better understand how these ecosystems are changing and how they can be protected for generations to come.”
Avalanches can pose a serious threat to people. They also play an important role in mountain ecosystems. However, surprisingly little research has been done on their effects on biodiversity, says Alba.
To better understand their impact on bird communities, Alba and his colleagues surveyed 240 points in the western Italian Alps near Turin during the bird breeding season in spring 2021. Half of these points were in areas previously reported to have been affected by avalanches or were historical data—some several decades ago and some within the last few years.
The data showed that habitats in areas where avalanches had occurred were more diverse — with more rocks, small trees, grass, and relatively short plants — compared to areas where they hadn’t. The differences are most pronounced at lower elevations, where tall trees such as beech, ash and maple grow most, compared to higher elevations, where larch and shrubs such as juniper and alpine roses are more common, Alba says.
As a result, researchers also found greater bird diversity in avalanche trails, with 62 species identified in previous avalanche areas and just 55 in unaffected areas, he says.
Among the birds seen in dense forests spared by avalanches were great spotted woodpeckers (Dendrocopos major), song thrushes (Turdus philomelos) and treecreeper (Certhia familiaris), he says.
In contrast, the avalanche areas contained a higher proportion of species that often live at the tree line at higher elevations, in addition to migratory birds and birds that typically nest in open habitats. These included black grouse (Lyrurus tetrix), tree pipit (Antus trivialis), linnets (Linaria cannabina), rock buntings (Emberiza cia), Whinchat (Saxicola rubetra), yellowhammers (Emberiza citrinella) and redstarts (Phoenicurus ochruros).
The composition of the different types varied even further depending on how recently — and how often — avalanches had occurred in a given area, Alba says.
Researchers are still debating whether global warming will make avalanches more or less frequent, but any disruption to their natural rhythm could have significant impacts on bird diversity, he adds.
“Any of these changes will have wider implications for mountain biodiversity, so it’s important to continue the research,” he says.
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