Tar and feathers: Clever crows trained to pick up cigarette butts in the big smoke

rows have been selected for the task because of their intelligence. Photo / Getty Images

A pilot scheme in Sweden could see flocks of the ingenious birds flying around city streets picking up litter in exchange for a snack.

A Swedish city is assembling a crack team of highly trained workers to combat the menace of discarded cigarette butts - its wild crows.

Flocks, or murders, of crows would fly around the streets of Sodertalje picking up butts and other small pieces of litter.

The birds will then drop them in a prototype container and be rewarded with a snack.

"By teaching the crows to exchange butts for food, they can help clean our streets and squares," says Christian Gunther-Hanssen, the behavioural economist who founded the Swedish startup Corvid Cleaning.

The company has selected crows because they are the most intelligent wild animals in Sweden.

"They are easier to teach and there is also a higher chance of them learning from each other. At the same time, there's a lower risk of them mistakenly eating any rubbish," Gunther-Hanssen said.

The birds trained so far have participated entirely of their own volition, meaning the scheme would "essentially be a barter", he added.

According to the Keep Sweden Tidy Foundation, a billion cigarette butts are left on Sweden's streets every year, with each estimated to cost as much two kronor ($0.32) to pick up.

Günther-Hanssen believes that if the scheme is successful, the municipality could save as much as 75 per cent of the cost of picking up butts, with crows able to do the job for a tenth of the price.

Tomas Thernström, waste strategist for Sodertalje municipality, told Sweden's TT newswire that he was seeking funding and looking for a suitable location for the food dispensers.

"We can teach crows to pick up cigarette butts but we can't teach people not to throw them on the ground," he said. "That's an interesting thought."