September 24, 2019
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Weather woes can make bird migration even more unpredictable

Migration is messy. It’s amazing that birds can find their way to the tropics in autumn, and then return to Maine in the spring without Google Maps. But as miraculous as it may be, things do go wrong.

Some birds simply get lost — mostly males, since they never ask for directions. Some overshoot their targets. For instance, summer tanagers have been popping up all over Maine this month. This red bird’s normal breeding range barely reaches New Jersey. Last week, one strayed as far north as Portage. Jen Brophy sent me the photo to prove it.

Most birds navigate just fine under normal conditions, but when are conditions ever normal these days? Songbirds migrate at night. It’s cooler, and safer from predators. Plus, they can navigate by the stars, or use the earth’s magnetic field like a compass, or both. However, they cannot control the weather. Maine is having a turbulent spring. Birds typically wait until the winds are from the south, allowing them to ride the breeze northward. This season, many of those favorable winds have come on the heels of unfavorable storms. During such events this month, radar showed that many birds took off just as the front passed, which means that the timing of their nightly departures varied unpredictably.

It’s been windy. Look at this from the bird’s point of view. Migrants destined for Maine have to skirt the east coast, being careful not to wander out to sea in the darkness. Meanwhile, the prevailing breezes tend to push them toward the ocean. As dawn approaches, the birds set down on land wherever they are, planning to rest and refuel. Imagine their disappointment when they discover that wind drift has pushed them out onto an island, surrounded by many other puzzled, hungry migrants.

What happens next is something called “morning flight.” As the sun rises, the birds see the mainland not too far away. Over there, they’ll find more room, more food, and more safety. So off they go — a stream of passerines crossing the water to reach the Promised Land. These flights are generally at low altitude, invisible to radar, so they have not been well studied until recently.

An impressive morning flight happened last Saturday, during the Wings, Waves, & Woods birding festival in Deer Isle and Stonington. As my morning bird walk gathered in the parking lot at Scott’s Landing, just over the causeway onto Deer Isle, we noticed a variety of warblers staging in the trees next to us. Paul Miller, executive director of the Island Heritage Trust, was first to point it out. One-by-one, and then five-by-five or more, the birds popped into the air and flew across the channel toward Little Deer Isle. We could look up in any direction and see a swarm of birds crossing.

The walk lasted 90 minutes. The stream of birds never abated. We tallied 16 different species of warbler, including less-common ones such as Cape May and Wilson’s warblers. Many alighted in the bushes near us before making the crossing. I’ve been birding a long time, and I’ve never seen a show like it.

Perhaps the most famous spot in Maine for this phenomenon is Sandy Point on Cousin’s Island in Yarmouth. In late summer, southbound birds get caught out on the islands of Casco Bay. Their morning flights get funneled over this one spot. Derek Lovitch of Freeport’s Wild Bird Supply skedaddles over there every time he sees a favorable breeze and good radar activity. He’s made it a habit to tally hundreds of birds, sometimes over a thousand, making the morning flight.

It takes a little practice to identify all the different birds when they’re a hundred feet up and flying away. Slowly, you learn to recognize the clues. Magnolia warblers have a distinctive two-tone tail that’s obvious from below. The flash of orange in a redstart’s wings stands out. Northern parulas are small, and the fiery throat is often visible from that angle. The black throat of a black-throated green warbler is obvious. A black-and-white warbler is black and white. And so on.

I’ve been weather-lucky this week. On the heels of the festival walk on Saturday, I led another walk at Leonard’s Mills in Bradley on Monday morning. It stormed overnight, but with winds from the south. The rain let up at daybreak, just long enough to allow a hungry horde of arriving warblers to swarm the treetops around us. It doesn’t get any better than this.

Bob Duchesne serves as vice president of Maine Audubon’s Penobscot Valley Chapter. He developed the Maine Birding Trail, with information at mainebirdingtrail.com. He can be reached at duchesne@midmaine.com.

 



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