A small flock of pigeons have been given tiny backpacks to monitor air pollution in London. The project was dreamt up by Plume Labs, a company focused on the environmental problem, and the marketing agency DigitasLBi. The rucksacks are fitted to the birds using small fabric vests, and the sensors inside are able to measure nitrogen dioxide and ozone levels. Only 10 birds are in flight at any one time, so the amount of data being collected is pretty small. However, it's still a creative way of analysing the air that millions breathe in every day in the capital.