Anthropogenic habitat loss, degradation and fragmentation are perhaps the greatest current threats to biodiversity in the tropics today. South Asia experienced widespread conversion of forest to agriculture in the nineteenth century, which makes it a particularly interesting area to investigate the relative persistence of understory insectivores compared to other guild In birds. Because of this evolutionary and ecological history, it is possible that Sri Lanka and the Western Ghats are lacking in numbers or variety of species in understory insectivores, which could make it difficult to see current differences between guilds in their sensitivities to human disturbance.

Researchers from Xishuangbanna Tropical Botanical Garden (XTBG), Sri Lanka and India tested the hypothesis by using data from a recent large scale study in Sri Lanka and the Western Ghats of India. In the region, transects were located in three different land-use intensities: buffer habitats consisting of degraded forest and agroforests, and areas of intensive agriculture. Beyond comparisons to other guilds, the researchers also looked at species interactions and the community structure of insectivores, as such community properties might be even more sensitive to human disturbance than the species themselves.

The overall species richness was found to be quite similar across the land-use gradient. However, densities were lower in agriculture compared to forest, and the proportion of insectivores, and particularly understory insectivores, dropped steeply from forest to buffer (on the boundary of reserves in degraded forest and timber plantations) to agriculture. No detectable differences in the slopes of mass-abundance relationships were found in the different land-uses.

The results demonstrated that insectivores and particularly understory insectivores were particularly sensitive or vulnerable to land-use intensification in Sri Lanka and southern India, which has a longer history of deforestation than other areas in the tropics. The researchers proposed that any unprotected forest fragments that have understory avian insectivores listed on the IUCN Red List , or the appropriate well-developed understory that these species prefer, should be a priority for conservation in South Asia and elsewhere.

The study entitled “The effect of land-use on the diversity and mass-abundance relationships of understory avian insectivores in Sri Lanka and southern India” has been published in Scientific Reports.

Contact:
Rachakonda Sreekar 
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences,
Mengla, Yunnan 666303, China
E-mail: sreekar1988@yahoo.com