Winter storms in spring a gamble for migrating birds

It’s only early April, still winter in Montana most years. Not this year, however, as spring is headed at us like a high speed freight train.

Meadowlarks are singing, lilac bushes are beginning to leaf, gophers are running around, and bluebirds are flashing their electric color in front of windshields.

Each one of us has a sign, a totem, a peg to hang our seasonal hat upon that signifies spring is approaching, that winter lies in the rearview mirror. And while we pay attention to the calendar and forecast, plants and animals are driven by daylight length.

That’s not surprising. Despite all the variables in the environment, long and short term, only seasonal day-length variation has remained constant since the beginning of this planet because of earth’s rotation on its axis around the sun.

Bird behavior, like migration and nesting, is influenced a bit by weather. Yet even last year’s wet and cold spring couldn’t stop bird migration for long.

And what do birds do when they arrive in Montana in early spring and find ice, snowdrifts and wind chills below freezing? Some die, of course, but many bird species have evolved over time to survive late winter storms.

Robins that had started to disperse to nesting areas go back into winter flocks. Others just hunker down. Areas around open water, like the Missouri River, can be warmer, or at least out of the wind, and hold insect life, which means food.

Most songbirds don’t start arriving this far north until May. Bluebirds are an exception, wintering from Utah and Arizona south through Mexico and arriving in north-central Montana in early to mid-March.

By the way, there are several fascinating Web sites on spring migrants. One of the better sites is hosted by the Cornell Lab of Ornithology and National Audubon Society at http://ebird.org/content/ebird. It lists weekly updates by regions, then species.

For a Montana flavor, specifically which bird is seen where, visit online at www.birdingonthe.net, then click on the North America link followed by regional under mailing lists. Finally, scroll down the page to Western U.S. and click on Montana. Bookmark it at that point.

Warm weather in early spring can draw out insects, a bounty to species like bluebirds. But a really bad spring snowstorm means the opposite, even killing bluebirds.

Red-winged blackbirds, robins and meadowlarks can survive cold, wet spring weather better than bluebirds, as they will find food near open water or on the ground. Even so, day after day of a lingering cold snap will take its toll on all returning migrants.

So why risk death just to be the first to arrive? The early bird gets the worm, of course. But also, the early bird grabs prime real estate for nesting, which means a better chance to hatch and raise young. Birds arriving too late are pushed into marginal habitat and are less likely to successfully nest.

So there’s the gamble — arrive early and with warm weather, or even average temperatures, thrive and prosper. Arrive late, or get hit with a cold wet spring, and lose. It’s a tough life, but most years it works.

Bruce Auchly is the information officer for Montana Fish, Wildlife and Parks Region 4.