Signs of Spring
By Jack Kintner
Some of the more interesting things in a mountain environment like the one we have around Mt. Baker are the changes that come as the spring season unfolds.
?Seasonal changes, in this case from February to June move both northward and uphill in a mountain environment, a few hundred feet in elevation being roughly equal to a few hundred miles in latitude.
This means that even though the amount of daylight is the same in a given latitude regardless of elevation, one can see a wider variety of the various markers and species as a season develops in the mountains as opposed to what those confined to flat country will see. All you have to do is move farther up or down the mountain. The rough dates given below are for elevations below 1,000 unless otherwise noted.
Lengthening of daylight hours is one of the first things that herald spring’s advance. At the equinox, which happens this year at 10:48 a.m. on March 20, the rate of the lengthening of days will be at its peak as the time between sunrise and sunset increases by almost four minutes each day. When daylight savings time kicks in on March 9 it will push the observed hour of sunset past 7 p.m., two hours later than it was just six weeks earlier (January 27).
Changes are also apparent as plants begin to wake up and birds begin to behave differently and in some cases move on north or arrive from the south. Plants provide food for the birds, or attract food in the form of insects, so the blooming of the one and the arrival of the other are closely related.
Prime time for wildflowers in the lowlands begins in March with the blooming of such things as the graceful satin flower in late March. In the high country some of the flowers bloom almost immediately after the snow leaves a meadow, such as the colorful carpets of white avalanche lilies or yellow glacier flowers. Sitka Valerian is found all over, from California to Alaska, and as might be expected can be seen blooming anytime during the season.
As with most migrating songbirds, the males are the first to arrive from their wintering grounds in Mexico, the longer days literally getting them singing. “The longer days produce physical changes in male birds,” said ornithologist Wayne Weber of Delta, B.C.,, “as their testes measurably grow in response to the greater amount of daylight.” The increased size generates hormones that produce mating and territorial behavior – singing and aerial battles over turf.
Some of the birds brought with spring are migrating through the area and others are seen all winter, like song sparrows that flit through creekside bushes, and chickadees that bounce around in the branches near bird feeders. Arriving male Red-wing blackbirds move in to claim their favorite haunts, and groups of robins are on the move. Robins winter from southern B.C. south to Mexico, and in the spring ours leave to go farther north and are replaced by others that winter farther south. By April, when most of the migrations peak, there will be places you can find at sunrise where the singing is so loud you would find it hard to use a cell phone.
As far as trees and shrubs go, the catkins on the alders begin to appear and give the leafless woods a purple cast by early February. Salmonberries and red-flowering currants are among the first touches of spring color in the woods and are a major source of nectar for rufous hummingbirds.
The early ones arrive in February, often in the middle of wintry weather that would seem to be too risky for the little birds. Weber explains that hummingbirds have a unique adaptation. “They go into a kind of overnight hibernation,” he said, “a torpor that lowers their body temperature and lets them survive. Otherwise it would take so much energy for them to shiver to keep warm, they’d starve to death.”
Just as there’s a first robin of spring, there’s also the first mosquito, seen in the lowlands in late February. Weber said that the arrival of violet-green and tree swallows correlates with the consistent presence of large numbers of flying insects, peaking in late February or early March.
Weber has cataloged the arrival dates (for Vancouver) of 104 species of birds, and said that over the years the dates have been gradually getting earlier.
Some plants attract food rather than providing it directly. When the big-leaf maples begin to flower in late April their blossoms attract insects, which in turn draws large numbers of warblers. Other species of birds arrive after the trees have flowered, evidently for the cover that their leaves provide for nesting.
Sapsuckers, a kind of slow-moving but impressively colored woodpecker that leaves those evenly spaced rows of holes in tree bark, migrate almost exclusively uphill and down rather than north and south. They’re more common above 3,000 feet, but can often be seen moving in groups through the lowlands in March and April as they migrate up the valleys. Look for relatively slow moving woodpecker-type birds that cling to tree trunks and that have dark red heads.
One bird that reverses the normal uphill in spring, downhill in winter migration pattern is the Blue Grouse, more often heard than seen. In winter they ascend in elevation and remain in the trees, subsisting on fir needles, then descend for the summer and stake out breeding territories. Weber said that he’s found four such territories staked out in North Vancouver’s sea-level Lighthouse Park.
Pacific tree frogs, the ones Hollywood uses for sound effects (just as they use the scream of a Red-tailed hawk for eagles), begin their “ribbit-ribbit” in the lowlands around the end of February and carry that on through April, or later at higher elevations.
The fun is in finding your own signs of spring, whether down low or up high in the hills as you search from when the trails open to when the last wildflowers appear, like the red monkeyflowers bloom in August. The last great show in the high country before the brief fall rolls into winter is the golden color of larches just before they shed their needles.
Expect more in the fall issue. |
