Prairie potholes and faltering flocks. As wetlands shrink, the numbers of migrating ducks plummet

NOVEMBER is the peak month for migrating waterfowl at the Bombay Hook National Wildlife Refuge on Delaware Bay. Visitors who flock to the refuge's 15,122 acres of tidal salt marsh, freshwater impoundments, wooded swamps, and grainfields to enjoy the spectacle have no difficulty finding ducks.

On a recent crisp, sunny morning hundreds of mallards, pintails, and other duck species blanketed Raymond Pool, an impoundment just a few steps from the refuge's headquarters. Paul D. Daly, the refuge manager, said he had witnessed an even more inspiring sight at Shearness Pool, the largest of the refuge's four impoundments, the day before.

``With the [number of] birds that were in there, it looked like the Serengeti Plain,'' said Mr. Daly, shaking his head with amazement. ``Unbelievable.''

The refuge's duck population for the 1988-89 season is expected to peak at about 16,000. But if visitors get the impression that Bombay Hook's apparent abundance of ducks accurately reflects how waterfowl are faring across the continent, they are wrong. North America's ducks are in serious trouble.

The US Fish and Wildlife Service estimates that some 66 million ducks will migrate south this fall - a number that is sharply lower than the fall flight of 74 million in 1987 and second only to 1985's record low of 62 million.

The reason for the alarming decline is the degradation or loss of wetland habitat in the vast prairie pothole region of the north-central United States and south-central Canada, North America's important area for duck nesting.

Much of the habitat in this so-called ``duck factory'' has been lost to agriculture in recent years. Urbanization and industrialization have also been factors.

As examples, 99 percent of the wetlands in Iowa have been destroyed, 56 percent in Minnesota, and 53 percent in North Dakota and South Dakota, according to the service.

The ducks' plight has been exacerbated since 1980 by prolonged dry weather, which has caused the disappearance of a large number of the potholes, most of which range from less than an acre to a few acres in size and are fed by runoff.

``We're very concerned,'' said Frank Dunkle, director of the service. Last spring, he said, ducks ``had no place to stop in wetlands and reproduce. They just didn't nest or flew on [farther] north and still didn't nest.''

Rollin D. Sparrowe, chief of the service's office of migratory bird management, said the potholes provide crucial habitat and food for ducks to raise their young, as well as cover to escape predation.

What's more, he said, ducks ``need these millions of potholes to carry out courtship behavior and keep pair bonding through nesting season as the hen gradually lays her clutch of eggs.'' If ducks are crowded together on fewer potholes, breeding is disrupted.

The duck species most dramatically affected have been pintails, mallards, and blue-winged teal, Mr. Sparrowe said, but gadwell and widgeon have also been affected.

The 1988 breeding population of pintails was 2.6 million - the lowest ever recorded and 54 percent below their average population from 1955 to '87.

Some species that do not nest in the prairies are also suffering. For instance, the number of black ducks in eastern North America has been declining for 30 years. The reason remains ``a mystery,'' said Bombay Hook's Daly.

Geese, on the other hand, are faring better than ducks, with fall flight numbers expected to equal or be slightly higher than last year's. Geese, which breed in the far north, typically nest on more permanent wetlands and are better able to protect their young from predation.

The Fish and Wildlife Service has shortened the 1988 hunting season and reduced bag limits in all four flyways - Atlantic, Mississippi, central, and Pacific. Mr. Dunkle said the restrictions should result in a reduction of at least 25 percent in the number of ducks killed, compared with the 1985-87 average, thus boosting the number available to breed next spring.

Dunkle pointed out, however, that curtailing hunting is not the long-term solution to the waterfowl crisis. He said the effects of this year's drought underscore the importance of the North American Waterfowl Management Plan.

The far-reaching plan, which was signed in May of 1986 by the United States and Canada, sets goals for protecting and restoring wetland habitat by the year 2000 through joint ventures involving federal and state agencies and private organizations. The money to carry out the plan - $1.5 billion - is to come from both the public and private sectors.

Joint ventures have been established for each of six ``priority habitat ranges'' - the prairie pothole region, the lower Mississippi Valley, the Gulf Coast, California's Central Valley, the lower Great Lakes-St. Lawrence Basin, and the Atlantic Coast.

The goal is to provide sufficient habitat to restore continental duck populations to their levels in the 1970s - 62 million breeding ducks and a fall flight of more than 100 million. Habitat restoration also will benefit geese and other wildlife.

The US portion of the plan was inaugurated Nov. 15 at the Upper Texas Coastal Prairie at Nome, near Houston. The project involves leasing about 1,000 privately owned acres of rice land as a protected site for the tens of thousands of pintails, blue-winged teal, mallards, snow geese, and other migratory birds that winter there.

The first Canadian project under the plan - a five-year, $5 million effort to expand wetlands in the 7,000-square-mile Quill Lakes region in Saskatchewan - was dedicated Sept. 27.

The plan is to be reviewed and updated every five years, with the first review set for 1990.

``The difficult times we're facing with the drought in the prairies and the [low] duck population right now furthers the need to move ahead'' with the plan, said Harvey K. Nelson, executive director of the plan's US office, in Minneapolis.

``One has to be an optimist in an activity like this. I'm really encouraged by the support that has built and continues to build across the country for this program.''

In the meantime, as days grow shorter and ducks settle in to await the time when they will once more journey northward, wildlife managers are asking a question only nature can answer: How much rain and snow will the prairies receive this fall and winter? So far, Mr. Nelson said, precipitation has been ``limited.''

``I think it's safe to predict that if we do not experience fall rains and normal or above-normal snowfall, we'll ... presumably be in worse shape, waterwise, in the pothole country than we were in the spring of '88. And the drought conditions would continue.''

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