They’re a flock of 10 pigeons, called the Pigeon Air Patrol, that fly around London and inform the Twittersphere of pollution levels throughout city. The idea was conceived by marketing company DigitasLBi and won Twitter’s #PoweredByTweets challenge last year.
http://www.cnet.com/news/pigeons-wearing-little-backpacks-tweet-about-air-pollution/
