Earth’s oceans twice daily rise around the world like a “wave” of people at a sporting event because of the pull of our moon’s gravity.

That rising and falling of the oceans’ tides as the Earth continually spins on its axis causes ocean water to fill and recede from seaside saltmarsh channels twice a day throughout the world, every day of the year.

The filling and emptying of saltmarsh channels along the North Atlantic Coast of the United States, for example, affects wildlife adapted to those channels. During warmer months, great egrets and snowy egrets wade after small fish in the channels’ shallows, while common terns and least terns dive for them from the air.

Ospreys, however, catch larger fish by dropping feet-first into the water from the air. They seize their finny prey with their curved, sharp talons.

But when the tide goes out, bare mud is left behind, which exposes aquatic worms, mollusks, and crustaceans, including the abundant fiddler crabs. Now other kinds of birds patrol the mudflats to find that invertebrate food in the exposed mud.

During spring and again in fall, little groups of migrant least sandpipers land on the mud like a handful of grain tossed across it. There they trot about, eating small invertebrates in the channel’s mudflats. In winter, flocks of dunlin, another kind of sandpiper, do the same when channel mud is exposed.

Ring-billed gulls eat exposed invertebrates from channel flats in saltmarshes in winter. And the striking and boisterous laughing gulls and beautiful red-winged blackbirds do the same in spring and summer. At that time, laughing gulls and red-wings nest among the tall grasses in the saltmarshes.

But I think clapper rails are the most interesting birds on exposed mud in saltmarsh channels along the Atlantic Coast through the year. These reclusive, permanent-resident birds and their fuzzy, black chicks hide among grasses in saltmarshes when the tide is in.

Adults have thin builds to slip easily through the grasses. They are brown with darker streaks, which camouflage them. And they have long, strong legs for running across the marshes and long beaks to capture invertebrate food.

The abundant clapper rails are far more often heard calling “kek, kek, kek …” than seen. And they are mostly seen moving slowly over exposed mudflats with their young to catch invertebrates when the tide is out, particularly fiddler crabs.

Saltmarsh channels are interesting when full of water or empty. They are well worth watching when the reader is at the shore any time of year.


Clyde McMillan-Gamber is a retired Lancaster County Parks naturalist.

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