A fledgling waterfowl group heads back to the Denman Wildlife Area this weekend with hopes of improving its nest-building success there before expanding into wetlands throughout the Rogue Valley.
The Southern Oregon Chapter of Delta Waterfowl plans to more than double the number of "hen houses" — nesting platforms — it constructed last year to help nesting mallards escape predators on the state-owned lands in the White City industrial park.
After finishing their job at Denman, the group will take its show on the road, building the low-cost, high-use duck condominiums and offering them as high-rise protection against foxes, coyotes and other predators to private landowners who want to help boost local duck production.
"After we get our Denman project done, that's our goal — to put them out where they're needed," says Steve DeBerry, who heads the Delta Waterfowl chapter.
The project already saw its first expansion earlier this month when chapter volunteers placed two hen-house platforms at the Medford Oaks RV Park in Eagle Point, DeBerry says. Predators there had devastated the local duck population, and the new structures are expected to elevate nests away from foxes and coyotes, he says.
For decades, waterfowl enthusiasts have installed wood-duck boxes to improve nesting success for these cavity-nesters throughout the West.
But mallards are altogether different critters.
Mallards nest in the tules and grasses around lakes, ponds and marshes. The nesting hens and their eggs are easy pickings for skunks, raccoons, foxes and all sorts of other small critters that have mallards high on their spring menus, rendering nesting success rates of about 20 percent.
After years of testing, Delta Waterfowl biologists created their hen-house design in the early 1990s. It's a wire-mesh cylinder stuffed with grass and suspended in a pond or wetland on a metal pole.
The heavy-gauge wire is strong enough to withstand the weight of a perched goose, but its 11-inch opening is too small for geese. The fresh grass provides a nesting space for mallards, which won't drag fresh grass inside like other birds do.
Suspending the hen house over water creates a formidable obstacle to ground predators. And the metal pipe means the most eager mammal would struggle to climb it.
DeBerry's crew installed a dozen of the structures at Denman last year, and their success rates seemed to track with what Delta Waterfowl crews have seen elsewhere.
The birds don't necessarily take to them right away, as the 30 percent use rate at Denman shows, says DeBerry. The hen houses that were used, however, had a 90 percent hatching success rate, he says.
"They were really successful for the first year," DeBerry says. "We expect success to climb this year as birds get used to them."
Delta Waterfowl studies elsewhere show an occupancy rate, on average, of about 80 percent after a few years, and their nesting success consistently ranges between 60 percent and 90 percent.
The most visible hen houses are those on Whetstone Pond adjacent to the Oregon Department of Fish and Wildlife's offices there, though they went largely unused, says Clayton Barber, the wildlife area's manager.
"That area gets a lot of public use, and it's probably more likely to have lower survival rates than others," says Barber, who believes Denman is home to more nesting geese than ducks.
However, DeBerry says hen houses along Whetstone Creek successfully housed six to eight hatchlings last June.
Delta Waterfowl volunteers have built 13 more hen houses for installation at Denman on Saturday, and plans are to move some of the unused structures to more out-of-the-way areas, DeBerry says.
Two more will be installed as part of a local hunter's senior class project, DeBerry says.
Reach reporter Mark Freeman at 541-776-4470, or email firstname.lastname@example.org.