Monday 23 September 2019

World's top insecticide 'makes songbirds anorexic'

Sparrows were among the birds affected by the sprays. Photo: PA
Sparrows were among the birds affected by the sprays. Photo: PA

Phoebe Weston

The world's most widely used insecticide could be driving dramatic declines in global songbird populations, research suggests.

Scientists say songbirds exposed to imidacloprid exhibit "anorexic behaviour" and delayed their migration because they needed more time to feed. This is likely to severely harm their chances of surviving and reproducing, the study found.

This research is the first to provide evidence of a link between a group of insecticides called neonicotinoids - applied as spray on most major crops worldwide - and the overall population declines observed in many migratory species.

Previously the toxic effects of neonicotinoids were only thought to affect insects.

"Our study shows that this is bigger than the bees - birds can also be harmed by modern neonicotinoid pesticides, which should worry us all," said Bridget Stutchbury from York University, who was involved in the study published in 'Science'.

Researchers looked at white-crowned sparrows who consumed small doses of imidacloprid.

Each bird's body was measured before and after exposure. A lightweight radio transmitter was attached to the bird's back.

They found birds given a higher dose of the pesticide lost 6pc of their body mass within just six hours. One dose caused birds to stay 3.5 days longer at the stopover site before resuming their migration, scientists found.

"Both of these results seem to be associated with the appetite suppression effect of imidacloprid. The dosed birds ate less food, and it's likely that they delayed their flight because they needed more time to recover and regain their fuel stores," said Dr Margaret Eng, the lead author on the study.

"Migration is a critical period for birds, and timing matters. Any delays can seriously hinder their success in finding mates and nesting, so this may help explain, in part, why migrant and farmland bird species are declining so dramatically worldwide," said study author Christy Morrissey, an ecotoxicologist from the University of Saskatchewan. (© Daily Telegraph London)

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