Competition for insects between ants and birds at the base of mountains could be driving the bird populations up to higher elevations, a recent study has found.

Oecophylla ant is an aggressive and dominant species known to prey on insects, and its population could indicate why diversity of insect-eating birds are more at higher elevations, researchers from the Centre for Ecological Sciences, Indian Institute of Science, Bengaluru, said.

They added that despite covering only 25 per cent of the Earth's surface, mountains are home to 85 per cent of the world's amphibian, bird, and mammal species, making them a highly diverse ecosystem and a key focus for conservation efforts.

Oecophylla ants are found at the bases of mountains in the tropical regions of Asia, Africa and Oceania. Previous studies found that the presence of the ant species at the base of the eastern Himalayas lowered insect population.

In the study published in the journal Ecology Letters, the researchers looked at whether the Oecophylla ant species affected other insect-eating populations across 46 broad-scale mountain regions, including the Himalayas and the Andes (South America).

Using publicly available datasets, such as those from the Global Mountain Biodiversity Assessment, the researchers analysed bird species observed at various elevations. The birds were categorised into dietary guilds -- groups of species with similar dietary requirements, such as insectivores and omnivores.

The bird species' diversity was found to be maximum at an elevation of about 960 metres.

The researchers said that the aggressive ant species are competing with insect-eating birds for food at lower elevations, thereby possibly driving the birds higher up in the mountains -- evidence they said was consistent with that from previous studies.

"In mountains, you often see hump-shaped patterns (of species diversity), and for a long time, people have been interested in why this happens. One of the mechanisms they did not think much about was biotic interactions like competition," co-author Kartik Shanker, a professor at the Centre for Ecological Sciences, Indian Institute of Science, said.

Other birds, such as nectar-eating and fruit-eating species, were found in reduced diversity at higher elevations, the researchers said.

Therefore, the presence or absence of the Oecophylla ants at the base of mountains could be a good predictor of why diversity of insect-eating birds peaks at mid-elevations, the authors said.

Except for the headline, this story has not been edited by The Telegraph Online staff and has been published from a syndicated feed.