Cats kill birds. Dogs chase cats. This is the fundamental premise of natural history, urban folklore and comic cartoons. “I tawt I taw a puddy tat a-cweeping up on me,” squeaks Tweety Pie, before leading Sylvester the Cat into the jaws of Hector the bulldog, or the thrashing broomstick of Granny.

Not so fast, Looney Tunes. The survey that we publish today suggests that dogs make even worse enemies to birds than cats. Dog-walkers with their dogs reduced the diversity of birds by 35 per cent, and their abundance by 40 per cent. Admittedly, this survey was carried out in scrubby areas on the outskirts of Sydney. But Australian birds are not notoriously more timid than European ones. And most cities have wildernesses where birds twitter and city dogs are let off their leads to chase their tails and defecate. Cats kill by creeping purposefully up on birds. Dogs evidently scare birds away unintentionally by their rowdy and unsavoury behaviour.

Most fundamental premises are flawed. And surveys are made only to confirm what we should have already suspected, if we had stopped to think. Nature is red in tooth and claw, in Surrey as well as Sydney. Songbirds come near the bottom of a bully chain, in which great creatures have little creatures on their backs to bite them. And so, ad infinitum. Bigger birds such as magpies and crows are also bloody pirates of fledglings. But holding the top of the chain comes the human dog-walker. He needs to be trained to consider the birds of the air as well as the pooper-scooper. Fish got to swim. And dogs got to bark. But the city is dead where no birds fly.