Coimbatore: Even dead trees play a vital part in maintaining a region's biosphere, say ornithologists. According to them, dead trees are usually preferred for setting up nests by certain bird species like the woodpecker and mayna. They make cavities in tree trunks for nesting. The same nest is reused by a host of other bird species during breeding. Removal of dead trees to plant new ones or for firewood can have a serious impact on the biosphere.
According to a research paper prepared by city-based ornithologist and senior principal scientist, P Balasubramanian on the 'Nest Tree Utilization by cavity Nesting Birds in the riverine forests in the Athikadavu Valley of the Western Ghats', dead trees in riverine belts are essential for cavity nesting birds. "Almost 32 of the 158 bird species are cavity nesting birds. These are basically birds which dig out a hole in the tree trunk with their beaks and make it large enough for the females to hide inside them," he said at Salim Ali Institute of Ornithology and Natural History's annual research seminar held at Tamil Nadu Forest Academy on Wednesday. "Cavity nesting birds are further classified into primary cavity nesters and secondary cavity nesters. While primary cavity nesters are those that actually dig out the trunk and create a nest, secondary cavity nesters use them once the original inhabitants fly away," he added.
Examples of primary cavity nesters are woodpeckers and barbets. "We excavated around 102 of the 302 nests recorded by us during our research and we realized that of the 102 nests, 94 of them were inside dead trees," said Balasubramanian, quoting his three-year research funded by the ministry of environment, forests and climate change (MoEF). "This is especially the case with Barbets, which have shorter beaks than the woodpeckers, so find it harder to dig out a cavity," he said. "They specifically prefer dead trees and their branches, because the cavity is a more brittle," he said. "These nests or cavities are again further used by plenty of secondary cavity nester species like the hornbills, mynas and parakeets. It is against their nature to carve out their own nests," he added.
The researcher pointed out that the absence of snags - standing dead or dying trees - would seriously affect the biosphere of the valley. "If all the dead or dying trees get cut for firewood or get destroyed during fires, these birds will find it difficult to create nests and if they don't do that, they will not breed. They will begin dwindling in number or just migrating away," he said.
The most preferred tree species, dead or partly dead, for creation of nest cavities were found to be the arjuna, mahua, mango and indian beech.
A lot of concern was also placed on the rapid loss of dense vegetation at the point where the Athikidavu River joins the Attapady Valley. "The area which is dominated by Southern Tropical Mixed Dry Deciduous forests has tropical semi ever green vegetation along the river," explained wildlife biologist with the nature conservation foundation, AJT Johnsingh.
"The map at the point where the river joins Kerala already looks brown, which means vegetation is thinning out. Action should be taken to plant indigenous species of trees in such zones," recommended both Balasubramanian and Johnsingh.
