Spare a ciggie?
I had thought that smoking a cigarette to ward off midges was an old wives’ tale. But recently I saw a rook at a motorway service station in Cumbria tearing a cigarette stub apart, before lowering itself onto the remains and rubbing its chest on the tobacco. Another rook joined it shortly afterwards and did the same thing. Does this odd behaviour have something to do with parasites? Roderic Mather, Via email
Jo Wimpenny responds: Various animals are known to ‘self-anoint’, applying various substances to skin, fur or feathers. Many birds will rub ants through their plumage to stimulate the insects to produce formic acid, which may kill feather parasites. The tobacco plant produces naturally high levels of nicotine, a potent insect neurotoxin, as a defence strategy against herbivorous insects. There’s some evidence that animals may utilise nicotine’s insecticidal properties; house sparrows have been observed building fluff from cigarette butts into their nests, and chicks that grew in these suffered fewer parasites than chicks in nests without the fluff. It’s possible that the rooks you saw gleaned a similar benefit , but it’s difficult to say for sure. It would certainly be interesting to explore this further!