GALLOWAY TOWNSHIP — Jeremiah Heise and Orrin Jones parked their pickup truck next to a flock of ducks snoozing in the sun at the Edwin B. Forsythe National Wildlife Refuge.

The skittish ducks went about their business up close and in plain view, oblivious to the truck and the researchers.

“This never happens,” Jones said, amazed.

The two graduate students from the University of Delaware are spending the next four months in separate bird blinds scattered across the refuge watching American black ducks and Atlantic brant — small geese found each winter in New Jersey — to learn how busy the birds are at night.

The federal study will determine how much marsh the waterfowl need to increase their numbers from Minnesota to Florida. But some nights, Heise said, they never even see a bird. Such is the life of a field scientist.

Still, the sprawling refuge is one of the best waterfowl habitats in the United States.

“To have wilderness land so near Atlantic City is amazing. Forsythe is quite a gem,” said Christopher Williams, a professor of wildlife ecology at the University of Delaware. He is supervising the study.

Black ducks and Atlantic brant thrive here in large numbers. But nationwide, black ducks have declined as much as 60 percent.

Black ducks were once the most abundant freshwater species in North America, but they declined from the 1950s through the 1980s. Federal researchers formed a task force in 1989 to find out why. The Forsythe study is part of that examination.

The ducks feed on fish and small invertebrates such as snails. They are notorious for their secrecy and wariness, spending much of the day in deep marsh cover and taking flight at the smallest disturbance.

“Black ducks used to be king of the ducks,” Jones said. “Now mallards are more common.”

A similar effort has been launched to study the decline of small geese, particularly Atlantic brant. Most of the 180,000 brant on the East Coast spend the winter in New Jersey.

Brant are vegetarians and form large flocks in the winter. These are the dark-colored geese commonly seen on protected bays or feeding on playing fields and golf courses across New Jersey each winter.

Just how large these flocks can get is the subject of the Forsythe study, a partnership of the university, the U.S. Fish and Wildlife Service and the New Jersey Department of Environmental Protection.

“The coast of New Jersey is very important for wintering waterfowl. Some of the largest concentrations on the East Coast occur in that area. We want to know what the landscape can support,” Williams said.

“If we’re not finding a lot of energy or habitat out there, that could be a true limiting factor for black ducks. At least it points to some very important land-management decisions. Do we need more coastal estuarine habitat? Could it be the quality of the habitat? Too much human development? All kinds of questions.”

Thanks to a keen interest in black ducks by hunting and conservation groups, much more is known about them than most other birds. But nearly all research has been conducted in daylight hours, leaving half of their lives a mystery.

“A lot of decisions about waterfowl management has been made on the assumption that duck behavior is consistent over 24 hours,” Jones said.

With military-driven advances in night-vision scopes, pitch-black darkness is no longer a barrier to field science.

The two-year study, which will wrap up this winter, is examining how much energy the ducks spend each night as they fly, sleep, swim, feed, preen and watch for predators. Previous research established the calorie consumption of each of these activities, Heise said.

Flying takes up 12.5 times the energy of resting for ducks and 13.4 times the energy in heavier geese, Heise said.

The scientists paddle canoes out to their marsh blinds where they stay each night from 9 p.m. to 3 a.m., scanning the water every 10 minutes with night vision to record what each visible duck or goose is doing at that moment.

A similar study examined the ducks’ daytime behaviors. The scientists will compare the results to tandem studies of the birds’ populations and the availability of food to establish the top densities that Forsythe or other marshlands can support.

Heise rolled up the window on the pickup truck to guard against the bracing wind.

“This is nothing,” he said. “It gets really cold on the marshes.”

One idea the students are exploring is whether the ducks and geese are spending more time feeding and moving around at night to stay warm. They often are seen sleeping in the noonday sun. This strategy also might help them avoid daytime predators such as bald eagles that could catch a distracted duck.

The researchers plan to publish their results in a scientific journal. The two students are using the study for their graduate theses.

Jones said he likes black ducks because they don’t beg for food like mallards, which are common moochers at suburban parks.

“They are truly a wild bird,” he said.

Contact Michael Miller:

609-272-7247