"It's July on Alaska's North Slope, and scientist Denver Holt is in Utqiagvik surveying nests. Denver has been coming here since 1992, and the snowy owls he studies have been coming here much longer: thousands of years. With its mix of coastal, low-elevation tundra and a rich presence of lemmings, the North Slope is the only area in Alaska where snowy owls regularly nest. How do snowy owls decide where they will nest? How do they manage to arrive...