Mudflats of South Beach for Shorebirds

At the close of last week's column, I alluded to the sandpipers as an invading army. This idea came from a friend, who was describing how a bird he had seen walked swiftly and stiffly across the ground. "They walked with a military step," he said. It was enough to clinch the identification he sought.

Every summer birders travel to favored shoreline spots to find the sandpiper army that sweeps through New England on its way from the Arctic to the tropics. We avoid the myriad of vacationers by finding the special places only the sandpipers go.

On Cape Cod, one of these places would be South Beach in Chatham. Several weeks ago a group of us hired a small boat to ferry us three miles south from Outermost Harbor, and drop us on the deserted barrier beach there. It was high tide, and many waders were resting on the higher flats out of reach of the water.

You would not know they were there until you set up your telescope and scanned a suspicious looking mass of lighter color. Then you would see a closely packed group of hundreds of small sandpipers, all standing erect on one leg, heads and bills tucked under their wings in silent mediation. Did they have thoughts of their impending invasion of the flats, or were their minds as blank as raw recruits?

If you approached too close to this standing formation, the heads would come out and the other leg would come down from its secret place. The one eye visible on the side of the head would be alert to danger, and the mass would begin to move as one, scurrying away across the sand. If alarmed enough, the feathered arms would spring into motion and bear them all far down the strand with a gentle note of complaint.

We stayed far enough away and tried to identify the varying kinds as they slept, the semipalmated, the least, or the white-rumped sandpiper. A bird would suddenly raise its head to preen a bit, keeping those precious flight feathers in shape. These "peeps" were by far the most numerous, but there were larger waders as well, the plovers, dowitchers, knots, and sanderlings; the yellowlegs, willets, and godwits.

The resting army was only the reserves. Already the scouts were marching on the flats where water met sand in the shallows of the estuary. Here on the protected side of the dunes away from the surf, huge mud flats lurked just beneath the calmer waters, and the waders were beginning their operations to overwhelm this territory. As the tide began to fall, the reserves rose as one and hurried out to join the attack, covering the flats.

With calm efficiency the different birds divided the task, the larger ones braving the deepest water, their heads bobbing and sweeping at the surface as long bills probed the mud beneath, extracting the wormy and crabby creatures living in the tidal zone. The medium sized birds patrolled the shallowest eddies, shorter bills picking at the receding pools. The small peeps spread across the wet mud, sometimes moving quickly from place to place, sometimes wandering about in seemingly aimless circles.

The same thing was happening at every estuary up and down the east coast. Three weeks later we watched them on the north shore at the mouth of the Merrimac River. They flew in tight flocks from their staging areas in the short grasses, weaving back and forth in dazzling drill, eager to descend when the muddy ground was first exposed.

We are always hoping to find a rare species among the mix of birds, but we are kept busy telling the difference between the least and the semipalmated sandpiper, the greater and lesser yellowlegs, the dowitcher and the Hudsonian godwit. Even for the experienced observer it is tricky, and for the beginner this family is a blur of legs and bills and body sizes. Most of them are camouflaged in shades of gray and brown, like the mud and water they inhabit.

Did you know we have estuaries right here in Hampden County? Next week learn about them and the battalions of waders that sometimes invade our peaceful backwater.