Of all the creatures we encountered today -- porpoises, whales, seals, sea lions, eagles, and mountain goats -- a small beautiful bird of forked tail and dancing singsong flight may be the most curious. The black-capped, red-billed Arctic tern is the world's greatest migrator, spending summers at high latitude in both hemispheres. These daylight-loving global ambassadors fly from nesting areas in Alaska and places further north to points as far south as Antarctica in boreal winter.

Other animals make long migrations to survive cold dark inhospitable winter seasons, but none go to the extremes of these terns. We watched more than three hundred harbor seals today floating on icebergs in front of the South Sawyer Glacier; they will soon disperse from this pupping area to widespread feeding habitats. We expertly spotted mountain goats high on steep hillsides; they make vertical seasonal migrations in response to snow cover and food availability. This evening in Stephens Passage we stood in silent awe listening to dozens of humpback whales blow in the still air then dramatically curve their bodies and lift their flukes out of the water repeatedly. These leviathans will swim 3,000 miles to warm water breeding grounds each winter. Yet none of these sojourns matches that of the Arctic tern.

Near the head of Tracy Arm, a 25-mile winding canyon-like fjord, we watched Arctic terns flit over silt-laden waters, perch on floating shards of glacier, call boisterously, and patrol their nests; they will travel over 22,000 miles a year between their near-polar seasonal residences, flying far offshore for months at a time. What drives this ultimate migration in search of long days and suitable foraging habitat? How can such a small creature survive such a long ocean-going journey? This incredible annual feat is testament to the marvel of migration and the wonder we have of the rhythms of the natural world around us.