Two black sea ducks float in the water. The ducks are mostly black, with a white patch on their foreheads and orange beaks.
Surf Scoters are among the numerous birds that pass through Maine on their annual migration south. The Schoodic Institute is conducting its "Surf Watch" count of the many species that come past Schoodic Point in Acadia National Park. Credit: Courtesy of Bob Duchesne

Weird things happen in Maine. Even if we spend most of our time enjoying the birds around home — even if we never explore the unusual things that happen elsewhere in the state — it’s fascinating to know what makes Maine birding special.

For instance, there is a natural phenomenon that happens at Schoodic Point in Acadia National Park every autumn.

Picture this. Northern Canada is a destination where millions of birds go to make millions of babies. In summer, it’s a Utopian source of food abundance for the birds willing to fly that far. In winter, it’s a frozen tundra where few birds can survive.

Between those two extremes, there’s a lot of movement. And that movement often passes right through Maine or along its coast.

Now consider this. There aren’t many people in northern Canada. Even if there were, the birds are nesting and they try not to be noticed. It’s mostly inaccessible, and almost impossible to study how breeding populations are doing.

But their numbers matter. Some of those birds are game species and require sustainable management. Many more are summer victims of a changing climate and winter victims of a changing habitat.

A lot of waterfowl nest across northern Canada. In autumn, the freshwater ducks and geese can migrate southward just about anywhere they want, settling onto lakes, ponds and rivers as needed. But the saltwater ducks are more narrowly confined to the coast.

Most are not deep divers. They primarily pluck their food from the bottom. That gives them a narrow migration corridor, constrained between dry land and deep water. In other words, many must fly right past Schoodic Point.

Schoodic Institute is there to count the birds as they go by. Not all of these waterfowl follow a coastal route. Some migrate over the interior, pausing on freshwater as needed. But enough stick to the coast that there is a representative sample passing Acadia National Park every autumn.

By counting these birds, and comparing year-to-year totals, Schoodic Institute contributes valuable data about species abundance. The project is called “Sea Watch” and runs from early September through mid-November.

Scoters are diving ducks that breed exclusively in the subarctic regions of Canada and Alaska. There are three species. Black scoters nest primarily east of Hudson Bay. White-winged scoters nest primarily west of Hudson Bay. Surf Scoters nest throughout both regions.

Even though these birds nest across more than two million square miles of Canada, in migration many will head straight for the Maine coastline. Some settle right here for the winter. Many more go all the way to Florida.

By standing in just one spot at Schoodic Point, biologists and volunteers can tally up and compare their numbers year-to-year, assessing population trends.  

I joined Sea Watch several times this season and enjoyed a few discoveries. For instance, not all the birds migrate at once. Common eiders are among the earliest to get going. Then there is another big pulse, possibly a wave from farther north, that arrives in October.

There’s a huge wave of double-crested cormorants in mid-October. That’s about the same time as the scoter wave crests. Meanwhile, a steady stream of northern gannets continues for all 10 weeks. They don’t seem to be in a big hurry.

Here’s one question you should ask yourself regularly, to make birds even more fascinating: “Why are they doing that?” I asked myself that question often at Schoodic Point while watching flight behavior under differing conditions.

Hawks are notorious for choosing a northwest tailwind to carry them south. Ducks don’t care. When the breeze is from the south and west, they get lift from the headwinds, and often fly higher. When the wind is from the north and east, they stay low, just above the water, getting a lift from the “ground effect” of being close to the surface. It’s the same boost that benefits aircraft during landing and takeoff.

Eiders, scoters and cormorants also fly in lines and vees, like geese, which reduces wind resistance for the trailing birds.

Wind direction also plays a big role in how close the birds get to shore. On any breeze from a westerly direction, they tended to be far out, flying on a direct line between Schoodic Point and the islands beyond Southwest Harbor.

On a breeze from an easterly direction, they get pushed closer to the point. Now I know which days to pick when I visit next year. And now, so do you.

Bob Duchesne, Good Birding

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.