Nesting city birds show it's not ifs but butts

Common wild birds such as urban house sparrows and finches have found a new use for an annoying source of litter. Some have started shredding cigarette butts into their nests as a way to repel biting insects.

Researchers from the Universidad Nacional Autónoma de México studied birds nesting on the university campus.

Almost 90 per cent of the 60 nests checked had cellulose cigarette butt material spread through them, and the team led by Dr Constantino Macías García believes the birds did this intentionally.

Volatile compounds

Biting bugs hiding in birds’ nests can play havoc, weakening the parents and reducing chick survival. For this reason many bird species living away from cities have an evolved behaviour to protect themselves.

They build fresh plants into their nests that “contain volatile compounds that repel parasites”, the researchers write today in the UK Royal Society publication, Biology Letters.

Picture the birds in an urban context where these plants are less available. The researchers believe the behaviour was repeated, but with the nicotine-saturated butts providing the volatile chemicals.

“We provide the first evidence that smoked cigarette butts may function as a parasite repellent in urban bird nests,” the researchers write.

They analysed the nests and also set traps to study levels of bug infestation. They found the bugs shunned nests with smoked butts but had no problems if they were unsmoked.

Bug repellent

The similarity between the use of green plants and the cigarette ends as nest material suggests that it “may indeed be an urban manifestation of a pre-existing behaviour”, they write.

The birds couldn’t have chosen better given nicotine is already used as a bug repellent.

Irish wild birds don’t seem to have cottoned on to this approach. “It is not something I have seen, but birds will incorporate whatever is available,” a spokesman for BirdWatch Ireland said yesterday.

There were, however, reports this spring from Boho, Co Fermanagh, about blue tits nesting in a wall-mounted ashtray outside a pub and last year something similar happened in Cambridgeshire in the UK.

The birds may have to come up with another plan if the Minister for Finance pushes the price of cigarettes above €10 a pack. That would be dear nesting material indeed.