Exodus of the resilient black crow follows flight of other wildlife from Iranian capital

This article is more than 11 years old

This article is more than 11 years old

Tehran's notoriously bad air pollution has long been a health hazard for its 12 million people, but now the toxic mix of fumes has sent a different set of residents fleeing – the city's black crows.

Environmentalists say the hitherto pollution-resistant population of crows have fled in large numbers in recent days after air quality reached crisis levels. Unregulated urban development has also destroyed the birds' habitats.

The crow exodus occurred less than three weeks after high levels of carbon monoxide and other gases in the air drove off other species of bird, including nightingales and pigeons.

Experts fear the departure of the crow – long decried in Iranian culture as a symbol of bad news and gossip – could be the death knell for wildlife in Tehran, where many plants have already lost their smell and colour as a result of the polluted atmosphere.

Mohammad Bagher Sadough, the head of the city's environment agency, said the crow exodus was a sign of a disturbed ecosystem. Eventually the remaining bird species will also leave, turning the city into an urban desert of high-rise buildings and traffic jams.

"Pollution is not the only element in the flight of crows and others birds, but it is among the most important," he told the Mehr news agency. "Habitats have been destroyed and the perpetuation of bird life has become impossible.

"The continued existence of crows, particularly with the departure of other birds, had given us hope that wildlife could survive in the city. With their migration that hope is fading and our concern over the destructiveness of urban environments has deepened."

Dr Jamshid Mansouri, an Iranian biodiversity expert, said the birds would be forced to seek new habitats in rural environments, where they were threatened by predators and possible extinction.

"If the process continues, eventually no birds will be able to live in Tehran," Mansouri added.

The polluted air is traditionally at its worst in winter, when a thick curtain of smog hangs over the city for days on end – frequently forcing residents to wear protective face masks. On occasions the poor air quality has prompted the authorities to close schools and urge people with respiratory ailments to stay indoors.

The city council estimates that 80% of the toxic gases are caused by cars, with large numbers of motorbikes compounding the problem. A new report by Tehran's Controlling Air Quality Company estimates that cars in the city emit 4,400 tonnes of pollutants each day.