Pesticide ‘makes migrant songbirds lose their way’

Controversial pesticides linked to the decline of bees may also be harming farmland birds, a new study shows

29th November 2017
White-crowned sparrow

Neo-nicotinoids – partially banned by the EU in 2013 – may cause migrant songbirds to lose their sense of direction, according to a new study.

Researchers at the University of Saskatchewan in Canada studied the effect on white-crowned sparrows of “realistic exposure” to two types of neonicotinoid, imidacloprid and chlorpyrifos.

They found in both cases, the birds lost their sense of direction.

And in the case of imidacloprid, the birds also “exhibited rapid and substantial declines in body mass and fat stores”, losing between 17% and 25% of their weight. They also showed “other symptoms of acute poisoning” including “loss of appetite… and death.”

Tested 14 days after exposure, the birds had recovered their sense of direction and their body weight.

But the scientists warned that the delay to their migration would hamper the birds’ chances of breeding.

Neonicotinoids are usually applied to seeds sown in the late summer or early autumn – just when many birds are gathering to migrate.

A separate study found evidence that seed spilt during sowing may be eaten by birds and other animals.

A spokesman for Bayer, which makes imidacloprid, told the Guardian newspaper: “Scientific evidence shows that imidacloprid has minimal environmental impact when used according to the label, including ingestion by seed-eating songbirds.” He added that the insecticide is applied to the seed hull – which­ songbirds usually remove before eating the seed inside. So in the real world, he argued, it was unlikely that birds would ingest the amount of pesticide given to the birds tested in the study.

 

Facts: Neonics

Neonicotinoids are designed to control insect pests that damage crops.

They affect the central nervous system of insects, leading to eventual paralysis and death.

They were developed by Shell and Bayer in the 1980s and 1990s.

Neonicotinoids were used for the first time in the UK in the late 1990s.

In 2013, amid growing evidence that they were harmful to bees, the EU banned three types of neonicotinoids – against the wishes of the British Government. The ban contained exemptions for certain uses.

Environment Secretary Michael Gove said on 9 November that the UK would support an extended ban on neonicotinoid pesticides, completely forbidding their use outdoors, but allowing their continued use in greenhouses. "The weight of evidence now shows the risks neonicotinoids pose to our environment, particularly to the bees and other pollinators which play such a key part in our £100bn food industry, is greater than previously understood," said Mr Gove.

 

The facts: Farmland birds

Farmland bird populations in the UK have declined by 56% since 1970, according to statistics from the Department for Environment, Food and Rural Affairs (Defra).

While the rate of decline has slowed, since the 1970s, the decline continues – between 2010 and 2015, the number of farmland birds fell by 9%.  

Much of the loss is thought to result from changes in agriculture – including a reduction in mixed farming and the loss of hay meadows and hedgerows.

 

Picture: Getty Images

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