In Seattle, the spring migration of birds brightens our days.



Many migratory birds travel by starlight, aloft in the night sky for hundreds and even thousands of miles to join us here.

Never mind the calendar — for some the arrival of the first swallow is when spring starts.

“To me it’s such a big signal,” said John Marzluff, author, biologist and professor at the University of Washington. “They come back in such swarms; they are just there all around and you realize you have been missing that all winter. It is such fun to watch them swooping and diving.”

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Take that, Twitter. The real thing, on display now all around Puget Sound, is sweet solace for the soul. Lie back in the long grass at the Montlake Fill near Husky Stadium, the green stems crushing sweet and verdant with that cut-grass scent, and watch the swallows dip and float. That is anyone’s birthright on our soft spring afternoons, as the sun comes and goes, and the clouds cruise by in a great gamboling parade.

Coming from as far south as Central and South America, swallows strafing the meadows, streaking across the skies and chittering on branches are just one of a panoply of spring migrants here now. Unlike many other migratory birds, swallows travel by day, to gorge in flight on insects as they go.

The spring arrivals are a diverse nation of color and song: yellowthroats, cedar waxwings, black-headed grosbeaks. Western tanagers, black-throated gray warblers, warbling vireos, barn swallows, tree swallows, to name just a few. And just now arriving, the Swainson’s thrushes.

“We refer to these birds as ‘our birds,’ but they spend the majority of their time either in transit or winter in Central or South America,” said Adam Sedgley, director of listener engagement and digital media for BirdNote, the national two-minute radio series about birds.

“We are so close to such rich diversity, it just reminds you of the larger cycle of life. There is no greater harbinger of spring for me than hearing the birds singing.”

Migration allows birds to avoid cold winters, and to take advantage of distant sources of food. But migration demands a conversion to a kind of superbird status every year, pumping up body weight in fat and shedding it at a spectacular rate once the exertion of migration is under way.

In human terms, according to the Smithsonian Migratory Bird Center, it’s the equivalent of a 150-pound person gaining 15 pounds of pure fat per day until tipping the scale at 300 pounds, then shedding 1.8 pounds per hour through vigorous exercise. A long-distance migrant such as a Swainson’s thrush will travel 125 miles a day all the way from as far as the tropical forests of Mexico and Central and South America.

So profound and hard-wired is the urge to travel in migratory species that even captive birds of their kind will be restless during the migratory season, fluttering their wings even as they stand in place, continuing the behavior for the same length of time it takes free fliers of their species to reach their destination. Poignantly, the caged bird will also face its ntended direction of travel.

Migratory birds are built for the task, with longer wings, bigger pecs, and the capability to fly from 500 to more than 2,000 feet in altitude. A higher concentration of red blood cells boosts their oxygen-carrying capacity at high altitude. Their respiratory system is also the most efficient in the animal kingdom, with a combination of lungs and multiple air sacs to provide a constant supply of fresh air.

Birds migrate by sight, primarily following the stars, and especially in poor weather, by sensing magnetic fields. Most travel at night both to avoid predators, and for celestial navigation.

On clear nights, atmospheric scientist and weather expert Cliff Mass at the University of Washington has picked up great clouds of migrating birds heading here from their southern wintering areas, an incoming shipment of color and song.

When the air is very clear, with no rain or other disturbance, migrating birds are plainly shown in Doppler radar, sweeping through the sky as night comes on, and disappearing as the sun comes up.

“As soon as it gets dark, all of a sudden the radar fills up with these echoes, and when the sun comes up, it all goes away,” Mass said. “It really is amazing. Birds are good targets, the bigger the better for radar reflection. They are much better than a raindrop.”

To Paul Bannick, a nature photographer and author of “The Owl and the Woodpecker,” the spring migrants are the miracle that comes every year, and a reminder of a world larger than our own.

“They have viewed lands we will never see, they have seen people that crossed our path that we were not aware of,” Bannick said, watching a colony of tree swallows tend nests on a snag at the Montlake Fill this week. “They are like travelers carrying their bag on a stick. What are their stories?

“They show us things; they remind us to stop and look.”

Lynda V. Mapes: 206-464-2736 or lmapes@seattletimes.com. On Twitter @lyndavmapes.