Baby ducks, born in recent weeks at Constitution Gardens on the Mall, never survived their first swim because predators from the sky and the lake snatched the tiny creatures as fast as they put their webbed feet in the water.

A similar fate has befallen nearly every duckling born at Constitution Gardens in the last five years -- a stark illustration of nature's food chain, according to the National Park Service.

Since mid-March, more than 90 baby ducks have rapidly become snacks for the bass and catfish in the 7 1/2-acre lake and the herons that have been drawn to the area because of the fish. But at the nearby and fish-free Reflecting Pool in front of the Lincoln Memorial, the duck community is thriving.

"As long as there's not a human cause for the problem, we try to let nature take its course," said Stephen Lorenzetti, chief of the Division of Resource Management at National Capital Parks Central. "You have some people who want to save the wildlife at all costs and that would be nice, but part of the goal is to keep the area as natural as we can."

The baby ducks rarely live more than 24 hours on the man-made lake. At least 30 more will hatch during the summer. None is expected to survive.

Doug Levine, a frequent visitor to the gardens off Constitution Avenue at 17th Street NW, has tried to persuade the Park Service to move the ducks to the safer Reflecting Pool. But because the gardens are federally protected, messing with Mother Nature is not allowed.

"There are about seven or eight other broods, and they'll get eaten just like the rest of them," said Levine, a duck lover who is also a broadcaster at Voice of America. "It would be nice to think that [moving them] would be a solution every time they're hatched. . . . I think the Park Service needs to deal with a problem that they don't see as a problem."

Constitution Gardens was created in 1976 as a living memorial to the U.S. Constitution. The pond was deliberately stocked with fish so city dwellers could have fun catching and releasing them.

Although ducklings live at the Reflecting Pool, the absence of baby ducks at Constitution Gardens is obvious. "Anybody who has walked by more than two or three times will notice there are ducks with no babies," Levine said.

He complains that herons are "flying in and taking over" and "upsetting the balance" of the gardens.

"Another 100 ducks [eaten] this year, 100 last, that adds up," he said.

Ted Woynicz, a Park Service volunteer who has monitored the situation at Constitution Gardens for five years, is an advocate for the ducks. He said 30 of them are permanent residents at the gardens -- and, just as if they were pets, he has names for most of them.

Astrid used to nest at the gardens, he said, but has now set up her nest at the Reflecting Pool, where her brood recently hatched. Eleven of the 13 ducklings are still alive, he said.

In contrast, two broods of ducks born at Constitution Gardens last Friday were gone by Saturday. And several weeks earlier, according to Levine, Cuyugo, a black-feathered hybrid, also lost her entire brood. He saw her taking the ducklings out for a swim. The next day, they were gone.

This is the first year, according to Woynicz, a waterfowl specialist, that a duck has finally found a way to protect her ducklings. Unfortunately, he added, the typical duck doesn't generally have the "brainpower" to figure out the connection between the fish and herons at the lake and their absence at the Reflecting Pool.

The Park Service lays most of the blame for duck fatalities on the catfish and bass.

"No one wants to believe what a fish can do to one of those ducklings," Lorenzetti said.

In 1989, catfish were deemed the culprits in the disappearance of a duck brood at Simon Bolivar Pond at 18th and C streets NW.

"There are certain species that have gotten stronger than the resident species," said Woynicz, who thinks an advisory board should work with the Park Service to reevaluate its policy against moving animals from the gardens. "Just out of a natural inclination," the stronger eat the weaker. "That's what they do."

CAPTION: Doug Levine studies destroyed eggs at Constitution Gardens. Ducklings thrive at the Reflecting Pool.

CAPTION: Herons like this one are drawn to the Constitution Gardens lake by the fish that are stocked there. Both the fish and the herons prey on ducklings. This year, one duck moved her brood to the nearby Reflecting Pool, where there are no fish.