A flock of pigeons wearing mobile phone-style backpacks are to be used as air-pollution monitors in the us, reports New Scientist.

The 20 pigeons will each carry a Global Positioning System satellite tracking receiver, air pollution sensors (capable of detecting carbon monoxide and nitrogen dioxide) and a basic mobile phone transmitter. Text messages on air quality will be beamed back in real time to a special pigeon "blog', or online journal, while miniature cameras slung around the birds' necks will post aerial pictures.

The pigeons are to be released in August into the smog-filled skies over San Jose in California. Beatriz da Costa, a researcher from the University of California at Irvine, and two of her students came up with the idea and had built a prototype of the pigeons' equipment.