Pesticides in Indian birds
Adam Halliday : Sun Feb 10 2013, 20:51 hrs
Earlier this month, when thousands of migratory harriers arrived at the Narmada, scores of ornithologists, conservationists, water management experts, forest officials, and organic farming lobbyists went into a huddle in Ahmedabad, India. Worried about changes in farming practices in regions surrounding the world’s largest roosting site for harriers in Gujarat’s Bhavnagar district, where an estimated 3000 birds of prey roost for six months post-monsoon, experts tried to chalk out a plan of action to prevent a decimation of this annual congregation due to pesticide levels.
Carnivorous avian species may be the worst-hit non-target organisms if India’s massive use of pesticides is not curbed or controlled, warns a recently published paper titled Status of Pesticide Contamination in Birds in India.India is currently the third largest consumer of pesticides in the world, consuming almost 44,000 metric tonnes in 2009.
In an examination of more than 534 dead birds of 56 species, 300 eggs of 37 species and 140 blood plasma samples of 16 species that lasted eight years, a team led by S Muralidharan of the Salim Ali Centre for Ornithology and Natural History, Coimbatore, detected varying levels of chemical pesticides.
The highest levels showed concentrations of DDE that touched 7,114 parts per billion, but others such as variants of HCH (hexachlorocyclohexane), endosulfan, dieldrin and DDT were also found.
Further, the 10 threatened birds included in the study showed contamination as well—a Nilgiri Wood Pigeon, which is considered vulnerable to extinction, for example showed 6,006 ppb of HCH and a 722 ppb concentration of endosulfan. “Detectable levels of total endosulfan were found in 75 per cent of the samples tested,” the study notes.
The blood plasma of a Sarus Crane, another vulnerable species, showed 286 ppb of HCH. The Nilgiri Pipit, a near threatened species, showed 142 ppb of DDT, while the blood plasma of another near threatened species, Painted Stork, showed DDT concentrations of 147 ppb.
The eggs of a critically endangered White-Rumped Vulture had concentrations of 6,160 ppb of the DDT, a major cause for concern after Diclofenac, used in veterinary treatment of cattle, nearly wiped out vulture populations across India.
“As recently as 1985 the species was described as ‘possibly the most abundant large bird of prey in the world’,” notes an IUCN assessment from 2012, and concludes there may be no more than 15,000 individuals now.
“When all the birds were grouped based on their food habits (frugivorous, granivorous, insectivorous, carnivorous, omnivorous and piscivorous) significantly higher load of pesticide residue was recorded in carnivorous birds,” notes the study.