An eastern towhee is shown in a leafy area. Credit: Bob Duchesne / BDN

Right this minute, birds are returning to Maine from as far away as the southern tip of Argentina. Weeks ago, our neotropical migrants left the pampas, the jungles, the highlands and the shores of South America. Along the way, they were joined by millions of birds that winter in Central America, the Caribbean and the southern U.S.

Not all migrating birds will travel this far. Others will pass through Maine, and keep on heading north. Every bird species is specialized, adapted to survive on certain foods and under specific conditions. If there are sufficient resources south of us, they’ll stop there.

I know. I just checked.

It all started at the end of March, following two Pfizer vaccines and a couple weeks of waiting. Finally able to spread my wings, in a semi-isolated camper van, I itched to go somewhere in April. My wife Sandi and I decided on the clever strategy of visiting Congaree National Park in South Carolina. From there, we would follow the migrating birds up the Appalachian flyway, until we all reached Maine at about the same time.

It didn’t quite work out that way.

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Congaree is 26,276 acres of preserved southern forest, the largest remaining intact bottomland in America. It’s awesome. I arrived just as some of the warblers did, right on schedule. Southern species, such as hooded and prothonotary warblers, were in full voice. Better yet, there seemed to be a northern parula in every tree. Although they do nest that far south, there were too many to all be resident breeders. Some had to be headed our way. Our timing was good … until it wasn’t.

After three days of great weather in South Carolina, it was time to head for North Carolina and the Blue Ridge Parkway. Alas, the weather turned cold and windy, bottling up the migrants. Discouraging headwinds persisted all the way up the Parkway, and continued along the Skyline Drive in Virginia. We were moving, the birds weren’t. Actually, that’s typical of spring migration. The timing of migrant arrivals in Maine is often affected more by the weather south of us, than it is by our own weather conditions.

Nonetheless, the experience gave me a new appreciation for range maps. Every field guide provides charts depicting where birds are in summer, winter and migration. A lot of Maine’s songbirds are adapted to life in a forest of mixed conifers and deciduous trees. While pines and hemlocks are common throughout the south, spruces, firs, tamaracks and cedars aren’t. Many of our songbirds nest only in the northern latitudes.

But there is an exception.

The higher elevations of Appalachia have a forest mix more akin to Maine’s. I was not far above Asheville, North Carolina, before I started hearing black-throated green warblers. Red-breasted nuthatches rarely nest below Pennsylvania, except for narrow fingers of elevation all the way down the ridges from New York to the Great Smoky Mountains. I could literally hear the habitat change as we ascended from the coastal lowlands, where summer tanagers proliferated, to the higher piedmont where scarlet tanagers took over.

Most amusingly, I witnessed firsthand the chickadee turf war. As a rule, black-capped chickadees nest north of the Mason-Dixon Line. Carolina chickadees stay south. There is a small mixing zone through parts of Pennsylvania, Maryland and New Jersey. But the black-capped chickadees own the ridges all the way down through North Carolina, while the Carolina chickadees dominate the lower elevations. Somewhere halfway up the mountains, they mix. The two species are similar, but they sing differently. You can hear the habitat change.

Another thing about range maps: generally, birds are less common around the edges of their mapped territories. Many bird species reach their northern limits in Maine. Eastern towhees, eastern bluebirds, Carolina wrens, red-bellied woodpeckers and blue-gray gnatcatchers all nest in Maine, but they’re not common. So I was astonished to hear towhees singing and calling at every stop, even in the worst weather — the most common bird of our two-week adventure. Carolina wrens came in a close second, seemingly everywhere. Bluebirds breed in Maine, but are mostly limited to fields and blueberry barrens. In the south, they are present in every habitat, from the bottomlands to the forested mountaintops.

The moral of the story is that range maps are a useful tool for developing your identification skills this spring. It’s a good time to bone up. If you know what species to expect in Maine this summer, you’re on your way to faster identification.

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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.