The signs of spring
By Warren Cornwall
Photograph by Gerrit Vyn
Spring is a noisy time in the Northwest. Marshes reverberate with the croak of frogs. The woods fill with the twitter of birds. Even the forest floor seems to hum with the white splashes of flowers. After months of long nights and gray days, Nature greets the sun with a shout. Come along for a brief sampling of spring awakenings, both loud and quiet.
When migratory birds like the Pacific-slope flycatcher arrive from southern climes, they might still be suffering from Zugunruhe.That’s the name scientists have given to a restlessness that overcomes some migratory birds as departure time arrives in the spring and fall. The flycatcher, a pint-sized gray bird dusted with yellow, overwinters as far south as Mexico. It returns to Western Washington to dine on insect hatches that come with spring.
Great blue herons that spend much of the year as solitary hunters flock to crowded rookeries beginning in February for a nesting season that can run into July. There, they mate and raise their young. But don’t get too close. During breeding season, herons sometimes abandon the rookery entirely if disturbed by people.
Douglas fir trees have a built-in thermostat and a remarkable memory. A Douglas fir keeps track of the amount of time it has spent in near-freezing temperatures and warmer weather during the winter, scientists have recently learned. That controls when the bud at the very top of the tree bursts in spring. If it doesn’t get cold often enough in the winter, the tree delays bud burst, which is crucial for growth. Scientists suspect this is a protective mechanism evolved to keep the tree from getting fooled into starting a growth spurt during a mid-winter warm spell.
Spring is coming earlier for algae in Lake Washington. Algae now bloom nearly a month earlier than in the early 1960s, due to warmer lake water. That could be a problem for other lake dwellers. Tiny water fleas called Daphnia that feed on the algae haven’t kept pace with the change, possibly because they hatch in response to some other factor, like the length of the day. Daphnia numbers have fallen by more than half. Daphnia are a critical food source for fish.
For other plants, it’s all about the sunlight. Take Arabidopsis thaliana (Thale cress), a small, thin-stemmed plant with white blossoms that grows in such common places as gaps in a sidewalk. University of Washington scientists have traced the molecular cascade that drives this plant to start blooming. It’s keyed to a dance between the plant’s circadian rhythm and light sensors in the plant’s cells. When those sensors detect enough light in the late afternoon, chemicals in the plant signal it to start flowering. While Arabidopsis is the lab rat of the botany world, the results apply to a wide range of plants, including important crops such as wheat and barley.the white-petaled avalanche lily. University of Washington scientists are enlisting hikers to help track the timing of these flowers and others to see how they respond to climate change.
Spring is still a long way off at higher elevations. At the Paradise area on Mt. Rainier’s southwest flank, spring doesn’t arrive until June or later. As the snow recedes, the first flowers to emerge are typically the glacier lily—a yellow flare of petals dangling from a long, slender stem; and their young. But don’t get too close. During breeding season, herons sometimes abandon the rookery entirely if disturbed by people.
Up on land, ponds start ringing with the insistent croaking of frogs. If you hear them,chances are they’re the Pacific tree frogs.The lime-green frog is found throughout Washington. It thrives in the woods and rural settings, but can occasionally be heard in various Seattle neighborhoods.
In the saltwater, Puget Sound’s southern resident orcas return from the open ocean along the West Coast in late May or June, following the first schools of spring Chinook salmon bound for spawning grounds. The orcas stay chiefly around the San Juan Islands and Georgia Strait during that time, because the main salmon runs then are in Canada’s Fraser River.
Meanwhile, 20,000 of the orcas’ bigger cousins, gray whales, are heading up the West Coast for feeding grounds near Alaska. But a dozen of the massive mammals make an unusual detour. In March, the whales head to waters around Whidbey Island. There, they spend two to three months feeding on ghost shrimp in shallow tidal flats before resuming their trip north. The visitors are so predictable, each has a name, such as “Patch,” who sports a white basketball-sized mark on its side.
In early spring, rough-skinned newts leave solitary winter homes beneath logs, rocks and leaves. They swarm over roads and fields, bound for nearby ponds where they can breed. Their bright-orange bellies might seem attractive, but beware: when threatened, these newts excrete a lethal poison from their skin.