The spring migration is over — birds have settled into their nesting areas for the summer.
Maine is a very special place for birds, and this becomes apparent when we dissect their large-scale use of various habitats throughout the state.
Thirty-three warbler species nest in eastern North America, and up to 26 of those species nest in Maine. Most warblers prefer northern climates, but 7 species consider Maine too chilly for raising a family.
Some of the warbler species that nest in Maine even have geographic preferences within our state. This is where it gets interesting.
The 45th parallel runs through Old Town, halfway between the Equator and the North Pole. Below this line, Maine’s forest is mostly deciduous. Above it, spruce, fir, cedar and tamarack become more common, with patches that resemble the boreal forest of northern Canada. As the forest changes, so does the mix of warblers.
You can visualize this transition zone by watching where the birds are. Blue-winged warblers are present but scarce, and only found in southern Maine. Louisiana waterthrushes don’t get much farther north than Augusta. It’s rare to find a prairie warbler beyond Bangor.
Some warblers that nest in southern Maine become more common, and even abundant, starting around Bangor. Blackburnian, magnolia and Nashville warblers are typical in this mix.
Meanwhile, numerous warblers that would be most comfortable in the Canadian forest find suitable habitat in northern Maine. Mourning and Wilson’s warblers are in this category, as are blackpolls.
Three species require boreal forest habitat for breeding. Cape May, bay-breasted, and Tennessee warblers nest in Maine’s northern and maritime spruce-fir forests, but barely. They can be difficult to find.
I relate this tale now because I just spent a week on Québec’s Gaspé Peninsula, above the 48th parallel — 100 miles farther north than Fort Kent. There, adjacent to the maritime influence of the Gulf of St. Lawrence, the forest is dense and coniferous. I couldn’t believe my ears.
Tennessee warblers were the most abundant warbler species I encountered. Bay-breasted warblers came in second. Cape May warblers finished third. In Maine, I must work hard to find these birds. In Québec, they easily found me. Meanwhile, some warblers that are common around here were unusual up there.
So, to look at the big picture, imagine a map of North America without borders — just a long string of forest types, from the mangroves of the Florida Keys to the stunted spruce abutting the Canadian tundra. Watch the transitions, as the tree species change with every mile north.
Now picture Maine, exactly halfway between tropics and tundra — with a climate influenced by mountains and sea. It’s one of the most dramatic transition zones on the planet. Maine’s mix of southern and northern songbirds is grand, and we often take it for granted.
It’s not just warblers. There are seven vireo species along the eastern seaboard. The black-whiskered vireo is stuck in southern Florida, but the white-eyed vireo has extended its range northward into Massachusetts. Someday, as the climate warms, I expect it to be a Maine bird. Meanwhile, yellow-throated vireos are only in southern Maine. Philadelphia vireos are only in northern Maine, but both are here.
The thrush family includes robins and bluebirds. Altogether, there are eight species along the east coast. One — the gray-cheeked thrush — flies right over us to get to its nesting grounds in Labrador and Newfoundland. It never breeds here. The others do. The wood thrush prefers the deciduous forest of southern Maine, while Swainson’s thrush likes the colder, damper forest of northern and coastal Maine. But they manage to overlap in a few spots.
Swallows? There are five east coast species. Maine has them all.
Woodpeckers? Ten species breed in the east. Eight are in Maine. The red-headed woodpecker nests no farther north than New York. The red-cockaded woodpecker nests no farther north than Virginia. The red-bellied woodpecker is a southern bird that continues to push its range deeper into Maine. It is no longer considered rare. Meanwhile, black-backed and American three-toed woodpeckers are denizens of the Canadian boreal forest. Maine has enough of that habitat that we can brag about hosting them, too.
Basically, most east coast songbirds can find habitat they like somewhere in Maine. The challenge for birders is to find that habitat, and then find the birds. Consider it to be a treasure hunt. Maine is blessed with mountains, plains, and coast. Maine has southern and northern forests. May as well enjoy it all.
