A community of birds of prey, insectivores, and seed-eaters is better safeguarded against climate change impacts.
A changing climate is posing threats to birds across Europe and North America by altering their habitats such as through changes in seasonal patterns that result in losses of their food sources.
Yet not all avian communities have been equally affected: bird communities with more diverse species in them occupying various niches have fared markedly better over the past half century than birds in functionally simpler communities, scientists say.
They reached this conclusion after examining nearly all North American bird species based on changes in their community composition and diversity over the past five decades.
Their results were unequivocal: avian communities with higher species richness and a larger variety of behaviours have changed less dramatically in the face of climate change.
“For example, if a community contained birds of prey, insectivores, and seed-eaters rather than birds from just one feeding guild, it was better safeguarded against the negative impacts of climate change,” explains Emma-Liina Marjakangas, a researcher at the University of Helsinki who lead the research.
The reason for this is that species diversity “works as a buffer against negative climate change impacts, especially during winter; i.e the season that has shown strongest climatic warming across the Northern Hemisphere,” the scientists note.
During the breeding season, they add, biodiversity played a smaller role, likely because bird communities change faster during winter than summer. This difference between winter and summer will probably widen as climate change speeds up, the experts say.
“Importantly, our results suggest that functionally diverse wildlife communities can mitigate effects of climate change by hindering changes in thermal niche variability, which underscores the importance of addressing the climate and biodiversity crises together,” the experts write.
Functionally diverse bird communities help maintain ecosystems by dispersing plant seeds, controlling insect populations and even pollinating flowering plants.
“Climate change reshuffles the composition of these important bird communities and therefore threatens their ability to provide ecosystem services,” the scientists point out.
“Habitat and available food determine a species’ flexibility for changing its breeding and wintering areas,” says Aleksi Lehikoinen, an expert at the University of Helsinki.
“For example,” Lehikoinen adds, “grassland species have shifted their distributions northwards slower than forest passerines, such as the American robin, or habitat generalists, such as the mourning dove.”
A key takeaway from the study, its authors stress, is that the biodiversity and climate crises will need to be “mitigated simultaneously to avoid multiplicative effects.”