Once a year, I punish readers with a column on shorebird identification. On the one hand, Maine witnesses a prolific shorebird migration; it’s a natural phenomenon to be celebrated. On the other hand, shorebirds can be devilishly difficult to identify. Most readers wouldn’t be caught dead on a mudflat. But some would, so here we go.

Maine is blessed with multitudes of shorebirds at this time of year. In spring, dozens of shorebird species race north to the Arctic to breed, mostly bypassing Maine. They’re in a hurry to get the best nesting spots and take advantage of the hellish explosion of insect life that accompanies snowmelt. But the season of abundance is short, and they all start heading south again in August. They’re not in a rush, and Maine’s coastline has more natural food washing onto the mudflats in August than it does in May. So huge populations of birds that nested clear across northern Canada get funneled through our coastline, some heading all the way to South America. That’s happening right now.

The problem for birders is that there are over 30 species of shorebirds that can occur in Maine. The typical guidebook lists 50 or more. Many resemble each other, and some are almost identical. How do you sort them out?

Actually, sorting is exactly what you need to do. Here are three ways to do it.

Sort by family. For convenience, let’s make three piles of birds: sandpipers, plovers and everybody else. Sandpipers have longer, skinnier bills. Plovers have shorter, heavier bills. Everybody else has a variety of distinguishing features, such as size and color, which make them look different from the typical sandpipers and plovers. Once you’ve guessed at which pile to put a bird in, identifying it gets easier because you can ignore the other two piles.

Sort by size. Least sandpipers measure barely six inches. Marbled godwits can top 1.5 feet. There are shorebirds of every size in between. Often, your first impression of a bird will be small or tall, skinny or fat, short-billed or long-billed, etc.

Sort by abundance. This is where a guidebook is often unhelpful. All birds appear equal. Each has its own listing. There’s no explanation of which is likely to be common on one particular mudflat. In reality, if you visit the mudflats in Lubec, most of the shorebirds are going to be least sandpiper, semipalmated sandpiper and semipalmated plover. (Semipalmated means partially-webbed toes.) These three species are all small – the smallest birds on the beach. There will be bigger birds there, too. Once you figure out the little ones, the bigger ones get easier.

A semi-palmated sandpiper and short-billed dowitcher search for food in August along the shore in Lubec. Credit: Courtesy of Bob Duchesne

Likewise, there are many birds in your guidebook that look nearly identical. Semipalmated and western sandpipers are strikingly similar, but westerns rarely occur in Maine. Snowy and piping plovers are akin to semipalmated plovers, but frostier. However, piping plovers are largely confined to the sandy beaches of southern Maine, and snowy plovers aren’t here at all. Short-billed and long-billed dowitchers are hard to tell apart in the guidebook, but long-billed dowitchers are seldom seen in Maine, especially Down East.

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So, looking at a bird on the mudflat, and then trying to pick it out of the 43 pages of shorebirds in The Sibley Guide to Birds, is exactly the wrong way to master shorebird identification. To make the job easier, we just sort them into piles so that we’re only comparing similar birds.

Most of the birds we see are going to be small. This grouping of small sandpipers and plovers is often called “peeps,” and it doesn’t take long to learn the tricks for telling them apart. Least and semipalmated sandpipers are close cousins, and both are abundant. Least sandpipers have yellowish legs, and are slightly browner. Semipalmated sandpipers are grayer, with dark legs. Semipalmated plovers will frequently flock with them. Sanderlings will appear bigger and whiter. Dowitchers will be bigger still, with long bills. But both will be smaller than the black-bellied plovers standing nearby. Whimbrels, willets and godwits will tower over all the others.

By the way, is there any group of birds with a stranger assortment of names? I haven’t even mentioned dunlin, killdeer, knot, turnstone, curlew, avocet or oystercatcher. No wonder backyard birders avoid mudflats.

You’ve got about two weeks to practice. By Labor Day, the current concentration will head south, and numbers will dwindle. Carpe Lutum. That’s Latin for Seize the Mud.

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.