"All five were ornamental chickens and couldn't get off the ground and the roundabout has no trees with low branches for them to escape from predators, " she said.
Both are far better at trapping heat than carbon dioxide, meaning that cows, chickens and their ilk have a larger greenhouse effect than allthe cars, trucks and planes in the world.
Tesco said its breakthrough was a "triumph" for the supermarket's programme to vaccinate all laying hens against salmonella, with attention now turning to wiping out traces of the bug in chickens.