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Thursday, March 8, 2001 - Page updated at 12:00 AM

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Spring: The birds know what it's all about - warmth and making whoopee

Seattle Times science reporter

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This is a story about heat, light and sex, much of it in the city.

It is an ancient story going back 100 million years and maybe more. Yet this drama is re-enacted every year, like swallows returning to Capistrano.

It's spring. Anyone walking outside yesterday could sense as much, with this winter's near-record dryness and yesterday's record 66 degrees in Seattle setting the stage for an earlier-than-usual budtime.

Of course, today we return to the classic Northwest minimalist forecast: cloudy, 50.

Spring here is a tease, a subtle narrative set in a climate so moderate that average daily temperatures between winter and summer vary by only 25 degrees. It's enough to make one wonder: Just what is spring?

It depends on where you look or whom you ask.

For Paul Lowenberg, director of the Puget Sound Science Writers Association and Seattle Mariner reporter for SportsTicker, "Spring is four words: Pitchers and catchers report."

Across the Western Hemisphere, more than 5 billion birds are moving north with the longer days. They are tugging at worms in warming soil and snatching roused and newly hatched insects. They have little more on their minds besides singing, eating, setting up a nest and making whoopee.

Of course, this plays out over several months. But if you want a specific date to peg as the start of spring, look for the arrival of the rufous hummingbird.

In a bit of news after the earthquake last week, Mark Ahlness and Janeanne Houston of West Seattle saw their first rufous of the year around 8 a.m. Sunday.

The bird reaches the Eastside on March 7, 8 or 9 - yesterday, today and tomorrow - says Diane Drisch, who has marked its return every year since she opened her Wild Birds Unlimited store in Redmond eight years ago.

"Invariably, those are the dates," she said.

For sticklers, spring will begin this year at 5:31 a.m. Pacific time on March 20, when the sun is even with the celestial equator, the line running from the equator into space. From that moment on, our days will be longer than our nights. Contrary to some long-held notions, we will actually be getting farther away from the sun in our elliptical orbit. But as the sun arcs higher across our sky and shines more directly on the Northern Hemisphere, we will warm.

"The seasons, like greater tides, ebb and flow across the continents," said Edwin Way Teale, who followed the season for his book, "North With Spring," published 50 years ago.

"Spring advances up the United States at the average rate of about fifteen miles a day. It ascends mountainsides at the rate of about a hundred feet a day. It sweeps ahead like a flood of water, racing down the long valleys, creeping up hillsides in a rising tide."

Migratory robins - some stay in place through the winter - start moving north in North America as the temperature hits 35 degrees, warming the soil enough to bring worms to the surface. Following the same temperature from California to the treeline of northwestern Alaska, a robin can spend two months in something of a biological time warp.

Spring peepers - small Eastern frogs - wait until the temperature is 50 degrees before peeping, Teale notes. Honeybees get active with the first pollen.

Around the Puget Sound region, great blue herons, their necks crooked like a plumber's J-bend, started nesting last month at the Kenmore Park & Ride and in woods south of the Ballard Locks. Pairs of outsized flickers and flocks of robins have been laughing and gamboling about for weeks.

Two bald eagles have been courting over Carkeek Park in Northwest Seattle, locking talons and falling hundreds of feet, the wind whistling in their wings.

Lynn Rachel Havsäll, a naturalist and director of Seattle's Camp Long Nature Center, has seen spring in the swollen buds of hazelnut plants, alder catkins and red flowering currants. Havsäll and visitors have been noting the changes in a log labeled "phenology," which marks the natural changes that come with the changing climate. Stinging nettles were 4 inches long Feb. 7 - you can eat them if you steam them enough - and the first Indian plum flower opened Feb. 14.

On Feb. 15, Camp Long's diminutive Polliwog Pond had the first lumpy mole-salamander egg masses, the gelatinous product of nocturnal "liebespiel," or love play.

Last week, the woods around the camp were a racket of song sparrows, Bewick's wrens - "drink your tee-e-e-e" - and chickadees, who have assumed a fast gargle as they grow aggressive and set out for breeding territory.

"Hearing this much noise in the woods at a quarter after 11 in the morning is definitely a sign of spring," Havsäll said, "because everyone is more vocal."

It's all a complicated, interwoven timing play, but it boils down to one thing.

"Spring is sex," Havsäll said. "What can I say? It's all about eggs."

Humans have a relatively muted response to the season. We tend to get more energetic, sleep less and eat less in a reversal of the winter dormancy tied to darkness.

But for animals like the rufous hummingbird, the season evokes an extreme reaction, particularly where sex is concerned.

This is not just any sex, mind you. This is honey-disconnect-the-phone sex. How else do you explain why a bird weighing one-eighth of an ounce would fly from Mexico to the Yukon, by far the longest Western migration for a bird of that size?

It starts in the brain, where the perception of lengthening days triggers hormones that stimulate migration and reproductive development - eggs, sperm and a cavalcade of other changes affecting singing, courtship and nest-building.

"The whole system is remolded each spring," said John Wingfield, a University of Washington environmental endocrinologist.

Its wings beating more than 40 times a second, the rufous times its migration to the blooming of flowers along the way: 50 species in California, 10 in British Columbia and five in Alaska. Around Seattle, the appearance of salmonberry and red flowering currant - the birds love red --means the rufous is not far behind.

The wave of hormones, particularly testosterone, is so intense in rufouses and other birds it threatens their survival. They fly and sing more, drawing the attention of predators. They run down their fat reserves. They get overly aggressive with other birds, including potential mates.

When its time to start parenting, birds turn off the juices nearly to non-breeding levels. Come summer, their reproductive system will revert to its infantile state, essentially rewinding puberty. Birds with bright "nuptial plumage" - like the American goldfinch, the Washington state bird - molt to muted browns and greens. Their gonads shrink.

Come next spring, their adolescence will return in a torrent. They will be young and amorous all over again, just like the very first time.

Eric Sorensen can be reached at 206-464-8253 or esorensen@seattletimes.com.

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