Cats, dogs, rats, sparrows and even humans are their victims; respectable neighbourhoods are transformed into scenes from Hitchcock or the Hammer House of Horror. By the time they have moved on, the streets are scattered with torn lumps of rotting meat. They are corvus macrorhyncos, better known as the jungle crow, and they are discreetly reducing Tokyoites to despair.
Put from your mind cuddly images of British rooks and ravens - at his biggest, corvus macrorhyncos is nearly 2ft from beak to tail, with a fearfully thick and powerful beak and prominent brow, giving him his characteristic look of sneering intelligence. Originally, jungle crows lived in the deep forests which still cover the more remote mountains of Japan, but in the past decade they have proved themselves to be uniquely talented urban citizens.
Thirty years ago, when there were just 3,000 of them, they were just a colourful aspect of Tokyo life, but today, with a population of 20,000 and rising, they are becoming an environmental problem. At a special symposium last month organised by the Wild Bird Society of Japan, hundreds of anxious ornithologists gathered to discuss ways of better "coexisting" with the feathered newcomers.
The problem can be summed up in a word: rubbish - the millions of tonnes of it generated in Tokyo every week. For mysterious reasons, Japanese do not use dustbins. Carefully sorted into "burnable" and "non-burnable", household and commercial waste is simply placed outside for collection in sealed bags. In places such as Osaka and Kyoto, these are collected overnight; it is no coincidence that neither city is bothered by crows.
But in Tokyo the refuse vans trundle through in the early light, by which time the flimsy plastic bags have been hungrily ripped open by the scimitar beaks of the crows. "A rubbish bag is just like a piece of wrapped meat," said Hajime Matsubara, a crow specialist at Kyoto University. "If we want to talk seriously about the crow problem, we first have to deal with the problems of Tokyo as a city."
And pavements littered with malodorous food are only the most obvious problem. In adapting to their new home, Tokyo crows have developed other bold and obnoxious habits. It is illegal in Japan to harm any wild animal or bird and, apparently as a consequence, the crows have shed much of their fear of humans, according to Hiroshi Kawachi, a school biology teacher who also studies the problem.
"In the forest, jungle crows nest high up - 20 or 30 metres - to be safe from predators," he said. "In Tokyo, they've started buildings nests just 10 metres up, in trees, telegraph poles and on high buildings." The problem comes when the arrival of baby crows brings out their parents' protective instincts - at such times, 10 metres is close enough for them to feel nervous and aggressive. As a result, there have been numerous reports of innocent humans dive-bombed by broody crows as they pass unwittingly beneath their nests.
"The interesting thing is that they only seem to attack weak targets - women or old people or children," said Mr Kawachi. The letters pages of Japanese newspapers regularly carry crow anecdotes relating other aspects of the creatures' resourcefulness and intelligence.
Like their human neighbours, crows in Tokyo are great commuters, roosting in suburban parks and then flying every morning into the city centre, where the pickings are richest. Apart from stealing jewellery from open windows, they regular fly off with wire coat hangers, which they incorporate into their nests. Their capacity for play seems to be highly developed, and the birds have been spotted climbing up and then whizzing down the slides in childrens' playgrounds.
In a letter to Yomiuri newspaper, one woman described seeing two crows on a wall, moving their heads from side to side with mysterious regularity. Cautiously, she peered over the wall herself - to see a tennis match, which the birds were following, to and fro, as avidly as spectators at Wimbledon.Reuse content