Great shearwaters are visiting the Gulf of Maine in September from their remote nesting islands, midway between South America and South Africa. Credit: Courtesy of Bob Duchesne

A funny thing happens in the Gulf of Maine this time of year. A whole bunch of northern birds are heading south for the winter. Meanwhile, a whole bunch of southern birds have come north, waiting for winter to end in the southern hemisphere. When the southbound birds meet the northbound birds, it’s a wonder there aren’t head-on collisions.

They all have one thing in common: They like seafood.

The Gulf of Maine is cold. Not as cold as it used to be, but still cold. Cold water holds more oxygen, which nourishes sea life, from tiny critters no bigger than a grain of rice to the giant whales that eat them. Birds flock from all directions to join the feast.

This is Maine. We have many boats, and many boat tours. Realistically, though, there is only one vessel that goes offshore far enough and fast enough to witness the full spectacle. In fact, Bar Harbor Whale Watch has the largest, fastest whale watch boats in North America. Even on a typical tour to see whales, you’re bound to see many exotic birds out there, if you know what to look for.

You may want to crack open a guidebook to see what I’m talking about. These are birds you will never see in the backyard. They are pelagic, a Greek word that means they are birds of the open ocean.

The biggest of these is the northern gannet. It nests in huge colonies in Quebec and Newfoundland. They dive from 100 feet in the air, hitting the water at 60 mph to grab fish. Such a feat would knock most birds senseless, but gannets have special air sacs around the neck and shoulders that act as shock absorbers. It’s quite a sight.

The northern gannet nests in huge colonies in Quebec and Newfoundland and visits the Gulf of Maine this time of year. Credit: Courtesy of Bob Duchesne

Wilson’s storm-petrels are the smallest birds out there, measuring only about 7 inches. These white-rumped black birds fly swallow-like just above the waves, daintily picking food off the surface. They nest on Antarctic islands during their summer, and come here during ours. Maine has its own species of breeding storm-petrel. The slightly larger Leach’s storm-petrel nests by the thousands on some of our coastal islands. Generally nocturnal, they are seen in daylight more often this time of year.

Red and red-necked phalaropes are marginally bigger than the storm-petrels. These shorebirds nest in freshwater wetlands around Hudson Bay in Canada, then form big flocks in the Gulf of Maine this time of year.

Shearwaters are in a family of birds that glide effortlessly above the waves, often so close to the surface that their wingtips shear the water as they bank into a turn. Great shearwaters are visiting from their remote nesting islands, midway between South America and South Africa. The smaller, darker sooty shearwater nests off the coasts of Argentina, Australia and New Zealand. A third shearwater is smaller than both. The manx shearwater is a North Atlantic breeder, nesting mostly in Europe. The northern fulmar is another northern breeder, similar in appearance and habit to its shearwater cousins. The nearest nesting colony is in Newfoundland.

Next come the trouble-makers. Several marauders chase and steal food from the other birds. Jaegers nest in the far north, most above the Arctic Circle. Though smaller than herring gulls, they are bullies, agile in flight and relentless in pursuit. They force gulls and shearwaters to drop their meals. Parasitic and pomarine jaegers are seen routinely offshore. The smaller long-tailed jaeger is a rare but annual sighting in Maine waters.

Two bruisers, related to the jaegers, also rob the other birds of their meals. Great skuas and south polar skuas are larger than the jaegers. The former nests around Iceland and a few sites in the British Isles. The latter nests along the coast of Antarctica. Skuas used to be uncommon in Maine waters, but their numbers seem to have increased. I was out with Bar Harbor Whale Watch a week ago, and saw three south polar skuas, in addition to 10 jaegers.

Oh, and while you’re looking for all these birds, enjoy the whales. On my recent trip, we chanced upon two mother-calf pairs. Much to our astonishment, the four humpbacks came together and swam up to the boat. Although their spy-hopping, tail-lobbing, fluke-flapping antics thrilled the crowd, they handcuffed the captain. Strict rules prevent the boat from getting close to the whales. But if the whales choose to approach the boat, there’s no option but to put the engine in neutral and wait them out. We did.

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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.