Last year, a 20-hectare section of Oahu Island in Hawaii was cut off from the rest of Oahu by a high-tech fence with a mesh so fine even baby mice can't get through it. Conservationists then removed all nest predators, effectively returning the land to its prehuman state some 800 years ago, when the island had no land mammals and millions of seabirds flocked here to breed undisturbed. Surveys show that the population of the point's colony of Laysan albatrosses has increased by 15%, to 400, since the fence was finished in March 2011. And the number of wedge-tailed shearwater chicks that survived and flew off tripled to 1775 in 2 years. This is good news for these oceangoing species, which, along with petrels, have been declining faster than any other category of birds.