The study, conducted outside protected areas in the Asian tropics, found that the agroforests support 204 bird species, including 13 endemic ones.
The researchers warn changing agricultural practices that open-up shade tree canopy or switching from coffee and areca to monoculture crops such as rubber, can "seriously damage" the ability of agroforests to shelter birds in the region.
The study, 'Producing Diversity: Agroforests Sustain Avian Richness and Abundance in India's Western Ghats' appears in the current edition of Frontiers in Ecology and Evolution. Coffee, areca and rubber are the most widely grown plantation crops in Karnataka's Western Ghats.
It points to the fact that these agroforests are being increasingly recognised for their "supplementary role" in conserving wildlife.
"We establish that coffee agroforests are substantially richer in birds than rubber and areca, but all three agroforests play an important role in providing subsidiary habitats for birds in the Ghats," said co-author of the paper and leading ornithologist, Shashank Dalvi.
"Large-bodied frugivores like pigeons and hornbills are found in much higher densities in coffee. These birds play a very important role of seed-dispersal and maintenance of forest trees in the region," Dalvi said.
According to conservation scientist Krithi K. Karanth, this is one of most comprehensive assessments of tropical bird diversity outside protected areas conducted in the world and shows a clear positive association of tree density and tree cover in the surrounding areas on bird diversity.
"This effort involved intensive research in 187 plantations covering an area of 30,000 km - taking the team two years to complete," said Karanth, lead author of the paper and associate conservation scientist, Wildlife Conservation Society-New York (WCS-NY).
Together, these three agroforest types cover almost 10,000 square kilometre and produce 258,000 metric tons of areca, 211,100 metric tons of coffee and 700,000 metric tons of rubber every year.
Highlighting that there is some evidence that areca growers in the region are switching to rubber, the authors cautioned, "We expect that, at a landscape scale, this will have significant impacts on bird communities as has occurred in Guatemala and Costa Rica."
"Policy decisions and markets must incorporate such biodiversity values and services provided by these agroforests to sustain and facilitate long-term biodiversity conservation," the authors added.
The study was a collaborative effort between scientists from WCS, Centre for Wildlife Studies, University of Wisconsin (Madison), University of Illinois (Urbana-Champaign) and Indian School of Business (Hyderabad) and supported by the National Science Foundation (USA).
Vishnupriya Sankararaman, Arjun Srivathsa, Ravishankar Parameshwaran, Sushma Sharma, Paul Robbins, Ashwini Chhatre are the other authors of the published study.
