Large seabird colonies have a surrounding boundary known as Ashmole's halo, where food sources are depleted, forcing the birds to travel farther to gather the food they need. The reason seems obvious—the more birds, the more they eat, which reduces the available prey. But that might not be the onl y factor at play, according to a new study of penguins and krill published July 15 in the Proceedings of the Royal Society B. ...read more read less