It seemed like a perfect morning: Bitter cold, a stiff northwesterly breeze and leaden skies. But for the first hour, we saw only an occasional duck winging over the small Chesapeake Bay finger cove we were hunting. My host, a fellow writer who grew up hunting waterfowl on the Eastern Shore, assured me the action would start in a matter of an hour or less.

He was right. What seemed like a vast, lifeless bay for the first part of the morning slowly evolved into a flurry of activity. A few seagulls started swirling over the water, occasionally diving on morsels of food. More gulls appeared. A bald eagle rode the wind toward a distant shoreline and a flock of geese winged across the narrow bay.

Then the ducks came. A line of canvasbacks sped just over the chop, and then banked hard when they spotted our decoys. We knocked down two, a drake and a hen, and soon after, the sky was buzzing with mallards, blacks and more Canada geese. Then flock after flock of bluebills appeared from our left, tiny strings of black dots that grew into identifiable birds as they closed the distance. Some kept pumping for other water, while others circled once, cupped their wings and dropped into the decoys bobbing in the waves in front of us. In a matter of a few hours, we had a pile of birds in the blind: a pair of canvasbacks, a couple of mallards and close to a limit of bluebills.

"So what got the ducks moving?" I wondered aloud.

"Tide's running," my partner noted, pointing to the water.

The mud bank three feet in front of our blind was now under water and the waves lapped at the posts. Broken bits of marsh grass, leaves and other debris floated by as if they were tumbling down an inland river. The tide was rising, all right, and the ducks and other birds knew it.

Teal move into tidal marshes to feed when the water rises.

The pull of the moon has a powerful influence on nature. Most notable is its effect on the oceans and the water directly attached to them. As the moon travels across the sky, its gravitational pull changes the level of the water. As the water moves, so do all the creatures that live in and on that water.

Changing Tides
Unlike birds that spend their time on still water and even rivers, tidewater ducks are constantly on the move because their preferred habitat either becomes too dry or too wet as the tides change.

"When I'm hunting a pond or some other still water, I can count on the ducks moving early and then shutting down for the rest of the day, especially if it's a bluebird day," said Mark Hoke, a veteran Chesapeake Bay waterfowl hunter. "That's not the case with tidal waters. Because the water is almost always moving, the birds have to shift around to find their preferred water depth and habitat."

Every duck species that lives in tidal water is affected by the constant up-and-down of the water, acknowledges Eric Peterson, a government contractor from Virginia. He warns, however, that nothing dictates waterfowl activity more than the weather, although tides and weather combined have a profound effect on waterfowl activity. Divers shift locations as food that was out of water becomes submerged again, and puddle ducks relocate as food or loafing areas either become too deep or are left high and dry by a receding tide.

"There is always something going on," Hoke said. "Even if there are no birds flying, you can be pretty sure that something will start flying as soon as the water starts moving. In most cases, it doesn't take long for a low tide to start coming in and a high tide to start moving out."