You might not know it, but birds—and especially tropical birds—have “comfort zones,” too. And members of the same bird species can have drastically different responses to deforestation depending on how close to their comfort zone they live.

According to research from Imperial College London, predicting a species’ sensitivity to environmental changes is crucial for developing conservation strategies. However, past assumptions about species’ sensitivity assumed that all members of a species would respond the same.

But the researchers found that this is not true. When investigating tropical birds in Brazil, they decided to see how different members of the same species responded to living at the edge of their range. These places tend to be less comfortable: they’re too hot or too cold, or they don’t have enough forest cover.

They analyzed 378 species detected over 200 sites that spanned 2,000 kilometers (1,243 miles) of Atlantic Forest in Brazil. When they did so, they found that there were dramatic differences in sensitivity to deforestation, depending on whether they lived near the center of their ranges or near the edge.

For 24 of the species analyzed, the researchers found that tropical birds at the edge of their range needed more than 50 percent forest cover to survive, while birds of the same species near the center of their range could survive on as little as 20 percent forest cover.

Study lead author Dr. Cristina Banks-Leite of Imperial College London said, “The dramatic variation in sensitivity to habitat loss we documented should have important implications for ecology and how we plan conservation efforts.”

With the results of their research in mind, the team found that at the southwestern edge of the region, the overall bird population was near the edge of its range, thus much more sensitive to deforestation. Fortunately, forest cover in that area is still quite heavy, and conservation efforts here should focus on restoring forest growth where needed and creating large reserves that preserve the current forests.

On the other hand, the northeastern part of the region is heavily deforested, but the majority of bird species there were more resilient to habitat change, primarily because those birds were at the center of their range—their comfort zone, as it were. In this region, the researchers suggested that the best conservation strategy would be to focus on species that have small ranges and are at immediate risk of extinction and figure out how to tailor conservation action requirements for those species.

“Our research with birds across the Atlantic Forest demonstrates how important consideration of species range can be when predicting species sensitivities and deciding on conservation strategies,” Dr. Banks-Leite said.

Photo: A Green-headed Tanager sits on a branch. This tropical bird species is one of many that are being affected by deforestation. Credit: Shutterstock