Five black duck hens flew into gray, snowy skies this week, wearing satellite transmitters scientists hope will give them key information they need to understand why black duck numbers are declining. They hope to learn about the ducks’ behavior and better direct conservation efforts and ensure ducks have the habitat they need, where they need it.

The birds were anxious to go after a night in captivity. Before being sent skyward, they first had to undergo standard body measurements and brave curious onlookers.

Ducks Unlimited biologist and University of Delaware graduate student Kurt Anderson fitted them with harnesses that hold the transmitters. The overnight stay in a Prime Hook National Wildlife Refuge building gave the birds plenty of time to preen their feathers over the harnesses, which are invisible and nearly undetectable under silky feathers.

Anderson said scientists keep the birds they catch together, because ducks need to stay with their social units. These five were captured together.

The transmitters are the latest in bird-tracking technology and much more efficient than old radio models, said Anderson.

“The satellite transmitters allow us to track these birds wherever they go,” he said. The little solar-powered boxes will communicate regularly with a satellite, giving scientists precise data and slashing the number of man-hours necessary to determine where the ducks migrate, eat and nest. That will be especially helpful because black ducks nest in remote northern forests.

Delaware Department of Natural Resources and Environmental Control (DNREC) biologist Matthew DiBona said Delaware is anxious to lend a hand in the project. “Black ducks are such an important part of our biology here in Delaware; it was an opportunity we couldn’t pass up,” he said.

Ducks Unlimited is alarmed black duck numbers are as much as 60 percent below what scientist predict they should be.

DiBona said scientists see fewer ducks on traditional wintering grounds, but know little about their migration routes, habitat use and breeding.

Anderson said information from this study will be especially important, because the last tracking data taken on black ducks came from a migration study done on banded ducks in the 1950s.

“We don’t know where they are going exactly and what they are doing,” he said.

The state contributed $30,000 to the project for the satellite transmitters and service.

Ducks are using reserves such as Prime Hook and Bombay Hook, some of the most critical wildlife habitat in the state, said DiBona.

“Ducks Unlimited and the state are very interested in habitat because habitat decides everything for these birds,” he said. Biologists want to determine how many birds wetlands can support, as well as how many ducks use them and how long they stay. “We know birds from all over use these critical stopover areas, so we need to determine how to direct our efforts to give them the food and habitat they need throughout the year,” said DiBona.

Food is critical. If birds arrive early in the season with good body weight, they can quickly reach a body weight healthy for reproduction and begin to nest. If something happens to the first nest, a healthy bird can possibly start another one.

Birds that arrive late or in poor condition may not have that opportunity, said DiBona.

DiBona said, “We want to track hens because the success of the species depends on hens.” Anderson said he looks for hens more than a year old. The trapping session at Prime Hook was successful, so they could be selective.

“We chose the heaviest hens. This is the lightest these birds will be all year as they battle winter weather, so through the rest of the year they will be heavier,” he said.

A higher body weight reduces the effect of the 22-gram transmitter on the birds.

Anderson said interbreeding between mallard and black ducks might be part of the reason for low black duck numbers, along with habitat decline, harvest and disease.

“Ducks Unlimited is really unique in that we let our science direct our habitat conservation efforts. We count on our state and federal partners to give us support,” said Anderson.

To learn more about Ducks Unlimited efforts to preserve black ducks, visit www.ducks.org/conservation/blackduckstudy/3410/blackduckstudy.html. Click on “Follow The Ducks” to watch the migration of tagged ducks.