At the humid edge of a mangrove swamp, on one of dozens of palm-fringed coral islands that fringe the Celebes Sea, a small greenish bird feels it.

On the sun-seared savannah of Tanzania, darting after insects stirred up in the dust by the hooves of zebras and wildebeest, a pale cinnamon bird with a black and white tail feels it.

In the teeth of a roaring Antarctic gale on the Weddell Sea, the gray ocean churned as white as the eroding summer pack ice against which it crashes, a lithe seabird borne effortlessly on the wind feels it.

As dusk falls along the Essequibo River in northern South America, and the first bats begin skimming the water's surface while a tinamou gives its last, plaintive whistle somewhere in the darkening forest, a slender, streaky olive bird settles into a sheltering clump of leaves for the night, and feels it.

Whether they spend the winter in the company of crocodiles and hornbills, lions and gazelles, leopard seals and penguins, jaguars and anacondas, the Arctic warbler, northern wheatear, Arctic tern and blackpoll warbler all sense the same growing tug. Scattered as they are across almost the entire globe, they all feel the pull back to Denali, back to the Alaskan landscape of their birth.

Right now, the spruces along Moose Creek where the blackpolls nest lay silent under snow; the winds howl unchecked through Thorofare Pass, where the wheatears sing in June. The tundra ponds are locked in ice, the willow thickets empty. Only the hardiest ones, the rock ptarmigans and the gyrfalcons, the ravens and gray jays, hunker down and tough it out.

But for the migrants, living their distant lives in distant places, the draw of the breeding season will soon make itself known; one day soon a little itch will awaken in them, which will become a compulsion, which eventually becomes the overwhelming, incontestable command: Fly.

And back they will come, as the snows melt and life returns to the tundra. And I'll be there, too, migrant that I am, because even here in the gentle mountains of Pennsylvania, where what we call winter has finally settled in, I can feel that same tidal force, that same growing itch that tells me it will soon be time to head back to Denali.

When the first Arctic warbler of the summer, freshly arrived from the hazy mangroves of the Philippines, begins to chatter its song from the willows - I will be there too, to welcome both of us home.

Author Scott Weidensaul will be at Camp Denali June 4-10 to share more on bird migration and conservation of Alaska's avifauna.