The Guardian reports that Iranian environmentalists say crows had seemed to be resistant to high levels of carbon monoxide and other gases that regularly hang over the city for days, especially in winter.

But the birds abandoned their urban homes for the fresher countryside three weeks after the oppressive air pollution drove off pigeons, nightingales and other species.

Iranian biodiversity expert Jamshid Mansouri told the newspaper the pollution refugees will be forced to seek new habitats in rural environments, where they may face unfamiliar predators and possible extinction.

Crows have long been an Iranian symbol of bad news and gossip.

Their departure accompanies changes in Tehran’s plants, which some say have lost their aroma and color due to the smog.

The Department of the Environment says about 80 percent of Tehran’s toxic gasses are spewed by cars and a large number of motorbikes that mainly operate without any emission controls.

Photo: Fars