Birds living in Indian mountains are suffering due to competition from ants

Competition with ants for food resources at lower elevations may be pushing these birds higher up the mountains.

In Short

• Traditionally, environmental factors like climate were thought to be the primary drivers
• Study suggests that biotic interactions, particularly competition, play a crucial role
• These results have important implications for conservation efforts

A new study from the Indian Institute of Science (IISc) has revealed an unexpected factor influencing bird species diversity in mountainous regions: the presence of Oecophylla ants.

The research, published in Ecology Letters, challenges long-held assumptions about species distribution patterns in mountain ecosystems.

Mountains, covering only 25% of Earth's surface, are home to an astounding 85% of the world's amphibian, bird, and mammalian species.

Traditionally, environmental factors like climate were thought to be the primary drivers of species diversity at different elevations. However, this new study suggests that biotic interactions, particularly competition, play a crucial role.

Led by Umesh Srinivasan, Assistant Professor at the Centre for Ecological Sciences (CES), IISc, the research team analyzed existing datasets of bird species observed across various mountain ranges.

They focused on the relationship between Oecophylla ants, known for their aggressive behavior and voracious insect predation, and insect-eating birds.

The findings revealed a striking pattern: in mountain ranges where Oecophylla ants were present at the base, insect-eating bird species diversity peaked at mid-elevations, around 960 meters.

This suggests that competition with ants for food resources at lower elevations may be pushing these birds higher up the mountains.

Kartik Shanker, Professor at CES and co-author of the study, emphasised the significance of these findings: "For a long time, people have been interested in why we see hump-shaped patterns of species diversity in mountains. One of the mechanisms they did not think much about was biotic interactions like competition."

The study also found that other bird groups, such as nectar-eating and fruit-eating birds, which don't compete with Oecophylla ants, showed decreasing species diversity with increasing elevation.

These results have important implications for conservation efforts, especially in the face of climate change. As Srinivasan warns, "If the ants shift their ranges
towards higher elevations due to climate change, this might impact bird species at higher elevations as well."

This research points to the complex interplay of factors shaping mountain ecosystems and highlights the need for comprehensive approaches to biodiversity conservation in these critical habitats.