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Mallards Establish Nests In High-Rise 'Condos'

DELTA MARSH, MANITOBA-Most of the hen mallards arriving on the prairie breeding grounds this spring will set up housekeeping in grass or brush, where 90 percent of their nests will be destroyed by marauding predators.

A few of the lucky ones will take up residence in predator-proof, high-rise condominiums known as Hen Houses.

Hen Houses are three-foot-long wire cylinders stuffed with straw and grass, and mounted on posts in small wetlands. Opportunistic mallards use the tunnels as secure nesting sites.

Research has shown that hen mallards nesting in artificial structures are much more successful than hens nesting in upland cover, and that's good news for ducks and duck hunters.

"The number of mallards hunters see each fall is directly related to what happens on the breeding grounds each spring," says Jim Fisher, who heads up Delta Waterfowl's Duck Production Program. "Unfortunately, what happens up here isn't always pretty."

Scientists say fox kill up to 900,000 ducks-mostly hens-each spring on the prairie breeding grounds, and egg-eating predators like skunks and raccoons destroy 9 out of 10 nests.

"Mallards and other puddle ducks nest in upland cover, often far from the nearest wetland," explains Fisher. "The hens and their nests are extremely vulnerable to predators during the incubation period, and even if the hen is successful, she must then lead her brood to the nearest wetland."

Delta's research has shown that Hen Houses enjoy up to 80 percent occupancy rates and nest success as high as 80 percent. And when the ducklings hatch, they just jump off the balcony and into the wetland.

"Hen Houses are likely one of our most cost-efficient management tools for increasing nest success," Fisher says. "That's important, because research has shown that nest success accounts for 43 percent of the annual variation in mallard numbers."

Fisher says he has erected 2,200 Hen Houses in Manitoba and another 400 in North Dakota. Four more super sites (100 Hen Houses) are scheduled for Manitoba, Alberta and North Dakota.

Mallards are the only upland-nesting ducks that use Hen Houses consistently, although Fisher says he's aware of scaup, canvasback, blue-winged teal and even the odd wood duck using them. "Mallards are very opportunistic," says Fisher. "They'll utilize a man-made structure, presumably to increase their odds of success."

Hen Houses are the mallard equivalent of the popular wood duck boxes that have been around since the 1930s. Nest structures similar to Hen Houses were first used in Europe, and later in the eastern United States.

Delta Waterfowl began experimenting with Hen Houses on the prairie breeding grounds in the 1990s. When studies conducted by Delta's Student Research Program showed how successful they were at thwarting predators, Delta became actively involved in erecting Hen Houses across the "duck factory". Delta chapters have gotten involved by building and installing Hen Houses in their areas.

"One member - Tom Dufour of Baton Rouge, Louisiana-got so excited about Hen Houses that each year he and other members of that chapter build 100 Hen Houses," says Fisher, "and each summer Tom and his wife drive them all the way from Louisiana to North Dakota."

Delta currently teams with the North Dakota Game and Fish Department, the Alberta Conservation Association, the Manitoba Habitat Heritage Corporation, and the US Fish and Wildlife Service to erect and maintain Hen Houses on the prairie breeding grounds.

For more information, including complete instructions on how to construct and install Hen Houses, visit www.deltawaterfowl.org.