AHMEDABAD: A study by Bombay Natural History Society (BNHS) has suggested that high-tension transmission cables should be laid underground in areas with a high concentration of birds vulnerable to collision. It also says that pre-development studies had indicated that wind farms set up for electricity could pose a major threat to migratory birds.
The study, “Review of existing global guidelines, policies, and methodologies for the study of impact of windmills on birds and bats: Requirements in India,” suggests that where it is not possible to lay underground cables, the authorities should mark overhead cables using ‘defectors’. Incidentally, the study mentions the incident in 2011 in which 76 Lesser Flamingoes and Greater Flamingoes were killed in the Gulf of Kutch when they came in contact with high-tension wires.
The BNHS study further suggests that construction in areas which have a high density of birds should not be undertaken during the sensitive period. In the case of migratory birds, it is important to keep their time of migration in mind.
The study further suggests that the forest department should consider ‘biodiversity offset’ elsewhere if development at a particular site cannot be avoided. Even windmills along the coast can be a major risk to large birds, the study says. (A ‘biodiversity offset’ is a method of demonstrating that an infrastructure project can be implemented in a manner that leads to no net loss or net gain of biodiversity.)
The risk is likely to be greater to foraging and roosting sites of birds or to migratory flyways or local flight paths, especially where wind power turbines intercept these species, says the BNHS study. Large birds with poor maneuverability are generally at greater risk of collision with structures while species that habitually fly at dawn and dusk or at night are perhaps least at risk as they are likely to detect and avoid the turbines. Collision risk may also vary for a particular species, depending on age, behaviour, and stage of annual cycle. The study reveals that in some cases, the number of bat carcasses retrieved, considerably outnumber those of birds.
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