They are the scourge of British streets and dubbed 'rats with wings' for their unhygienic habits.

But scientists believe an army of urban pigeons could be recruited to help prevent the spread of disease and toxins by acting as constant 'biomonitors.'

The feral birds have an unedifying reputation as pests, but their ability to spread out and occupy all parts of a city could be harnessed to keep track of toxins and diseases which damage human health, say experts.

Rebecca Calisi-Rodriguez, of the University of California, believes pigeons are a perfect tool for monitoring dangerous pollutants because they live off human waste and are therefore inhabit same areas as city dwellers and are exposed to the same contaminants.

The California team said pigeons could serve as 'the proverbial canary in the coal mine' because they 'walk on the same pavements, breathe the same air and eat the same food as humans.'

"Pigeons have existed for ages in close proximity to us, eating the same food, drinking and being exposed to the same water sources, soil, air, pollution," said said Dr Calisi-Rodriguez, associate professor of neurobiology, physiology and behaviour.

"They have a very small home range, spending the their life within a few neighborhood blocks. And because they are alive they process these chemicals in their bodies.