There are 5 billion songbirds leaving Canada right now, heading toward the tropics. Millions of Maine birds are leaving, too. It’s a river of birds. What a spectacular sight to see!
Except that you can’t see it.
Larger birds migrate in daylight. Hawks need the sun to warm air masses, lifting the birds over obstacles. Geese honk their way south in V formations. Double-crested cormorants do likewise, though silently. You can see all of this.
But songbirds migrate at night. The air is cooler, the winds are kinder, and the darkness is safer. Predatory hawks don’t hunt at night. The celestial night sky aids navigation. Days are for feeding, nights are for flying.
When weather conditions are right, many birds in a region take off together and travel in small flocks. They keep assembled by uttering flight calls, short notes that are unique to each species. Sometimes, on a good night, you can hear them flying over. It may be just a few “cheeps” per minute, but it goes on until dawn. At first light, they settle down to feed and nap. You can hear the river pass over.
All rivers have eddies where currents swirl around obstacles. There are choke points on migration routes where birds become particularly concentrated. Spring migration is famous for fallouts — places where birds first encounter land after crossing seas and large lakes. In urban areas, green spaces attract birds as they are settling down after a night flight. Large city parks and cemeteries are famous fallout points.
Most birds are reluctant to fly over water. If anything goes wrong, there’s no place to land. Now imagine the river of autumn birds that flows into Nova Scotia from northern Canada. The birds wend their way southward, only to find that they’ve run out of land at the southern tip. It is likely that they explore the coastline, looking for the shortest route across the Bay of Fundy to Maine.
That route takes them over some of our offshore islands. Matinicus and Monhegan are obvious places to touch down. Metinic is an island near St. George that is proving to be a big stopover. Maybe huge.
Concurrently, there are birds from New Brunswick and Quebec that are flying south along the Maine coastline. We have our own set of bays they must fly over. All of these bird rivers converge in certain places, and sometimes the morning after a big flight can be pretty spectacular.
One particular spot in southern Maine has an autumn reputation. After a night of migration, whole flocks of songbirds discover that they’ve settled down on one of Casco Bay’s islands by mistake. They become anxious to return to the mainland, and this crossing tends to concentrate at Sandy Point Beach on Cousins Island.
Derek Lovitch owns Freeport Wild Bird Supply. He has made it a habit to visit this spot over the years. Mornings where there is likely to be high bird traffic generally follow a clear night of northwest breezes. And so it was last Monday. The day dawned with a 40-degree temperature and a 13-mph breeze from the northwest. For four hours, Derek counted the birds crossing the point.
Identifying a flying warbler at a distance is difficult under the best of circumstances, but Derek is good at it. He spotted 265 northern parulas making the crossing. There were 122 black-throated green warblers, 103 yellow-rumped warblers and 71 blackpolls. Most American redstarts have migrated by now, but 24 made the crossing that morning. Palm warblers are late migrants, and many haven’t left yet, but Derek counted 47. Northern flickers are easy to pick out, because of their large size and white rumps. Derek noted 115 crossing to the mainland.
Altogether, Derek tallied 45 species and 1,348 individual birds crossing the causeway at Sandy Point Beach during the four hours. That may seem like a lot, but he reports that this wouldn’t even make the top 10 list of days he’s spent on that beach.
A few rarities turned up. Dickcissels are grassland birds of Middle America that don’t breed in Maine or anywhere near Maine. I’ve never seen one here. Derek got two during the morning. I’m envious. He counted 10 Tennessee warblers. That’s about nine more than I’ve seen all year. My envy grows. There were 345 birds that were too distant to identify. My envy shrinks. Counting this river of birds is starting to sound like a lot of work.
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 email@example.com.