National Public Radio: The further north an arctic shorebird flies, the less likely it is that a foxy predator will gobble the eggs in its nest. A new study suggests that’s one reason why some migratory shorebirds like the white-rumped sandpiper are willing to make exhausting annual journeys that can be more than 18,000 miles round-trip, from their wintering areas at the southern tip of South America to their breeding grounds in the Canadian Arctic. “Their migration is a pretty amazing feat,” says …