Elevating Mallard Production

Decades of rigorous research have shaped Delta’s Hen Houses into the proven, mallard-making structures they are today

Decades of science show that ducks have a problem: Study after study affirms that nest success in many areas of the breeding grounds isn’t even meeting the threshold needed to sustain duck populations, let alone increase them. Not only are the vast majority of nests failing because predators find the eggs and eat them, but sometimes the nesting hen is killed, too.

Given the impact of overpopulated predators on duck populations, it’s not surprising that Delta Waterfowl has been studying duck nest predation for as the long as the organization has engaged in waterfowl research. H. Albert Hochbaum, Delta’s first scientist, quickly recognized that duck populations and recruitment are closely tied to nest success. Lyle Sowls, Delta’s second-ever graduate student, specifically studied the effects of nest predation by Franklin’s ground squirrels at the Delta Marsh in 1939.

Their genius in exploring these issues played a part in the development of a tool that, nearly a century later, is being used by Delta Waterfowl as it strives toward its Million Duck Campaign goal: To produce one million ducks, every year, forever.

Here is the fascinating story of the Delta Hen House.

Predator Problems
Predation has always been a fact of life for ducks on the prairies of Canada and the north-central United States. However, during the past 100 years, major changes to the landscape have magnified the impact on nesting ducks. During the 1930s, nest success of 35% was common. But, since then, continued wetland habitat losses and disappearing upland grass cover have exacted a heavy toll on ducks. At the same time, predator populations have changed and surged, further compounding the problem.

Populations of red foxes, the most efficient duck nest predator on the prairie, exploded in the 1970s. Raccoons, which were previously non-existent on most of the prairie, expanded northward and have thrived in agricultural regions ever since. Skunks, too, became much more numerous. Working farms and ranches provided new sources of food and cover for predators, all while reducing nesting cover for ducks in favor of grain crops.

Less habitat with more predators is a bad recipe for nesting ducks.

The U.S. Fish and Wildlife Service reported results from a study conducted from 1969 to 1973 that estimated that 900,000 adult ducks—mostly nesting hens—were killed by predators on the prairies each spring. In addition, several other studies showed that duck nest success was as low as 5% to 10% on many areas of the prairie—well below the 15% to 20% rate needed to prevent duck populations from declining.

As the 1990s began, Delta’s leaders were actively working to conserve high-quality duck habitat in the United States and Canada through programs like Adopt-a- Pothole. However, they also could see that the mounting loss of breeding habitat and a proliferation of predators would remain a reality in the prairie pothole region, even as key incentives for landowners provided in the U.S. Farm Bill were making an enormous difference for waterfowl in the United States.

Most waterfowl managers had inklings that efforts to reduce nest predation could help ducks, but who would do it? And how? In the 1950s, Delta’s assistant director, Nan Mulder, crafted woven “nest baskets” that helped inspire today’s Hen Houses.

Duck Production Tools Emerge

Delta has never been afraid to search for solutions to problems facing ducks. That’s why, in 1994, predator-control research began at a pair of 16-square-mile wetland blocks in Towner County, North Dakota. Over four months, researchers removed predators from a 10,000-acre test block, resulting in a 45% nest success rate compared to just 14% in the non-trapped control block. While this finding may not have directly influenced Hen Houses, it did suggest that Delta was on the right track in considering the impacts of predators on duck production.

This must have been motivating for the Delta scientists and students who, during this same time period, had already begun researching Hen Houses as tools to make more ducks.

The use of artificial nest structures for waterfowl began in Europe but became popular in the United States through the work of Art Hawkins, Frank Bellrose, and the Illinois Natural History Survey in the 1940s. Bellrose and Hawkins studied wood ducks on the Illinois River Valley. They erected hundreds of nesting boxes designed to be hung in trees and on poles for the cavity nesting wood ducks.

Hawkins, a graduate student of Aldo Leopold, left Illinois behind in 1946 after being hired by the U.S. Fish and Wildlife Service to develop a comprehensive breeding duck survey. Hawkins was stationed at the Delta Marsh for eight years, where he worked alongside Nan Mulder, a Dutchman who served as assistant director of the Delta Waterfowl Research Station. Mulder was Delta’s “decoyman,” operating a mammoth device to lure ducks into a long funnel to be caught for study and banding. During his time at Delta, Mulder also fashioned nest baskets for ducks, and several images in the Delta photo archives show them in use.

“Mulder’s nest baskets were hanging in trees all over when I first came to Delta,” Dr. Robert Bailey, a Delta student beginning in 1970, said in an interview for the book, Delta Waterfowl: How The Duck Hunters Organization Shaped Waterfowl Conservation in North America. “He wove nest baskets out of reeds like they do in Holland, so he was very likely the influence for Hen Houses.”

Mulder’s nest structure design certainly was a consideration for Delta’s biologists in 1989, when board member Jim Scheer of Illinois brought forth the idea to consider placing them on wetlands in Canada. Scheer had seen deployment of nest cylinders by the Iowa Department of Natural Resources and championed their use in conjunction with Delta’s Adopt-a-Pothole Program. The first Delta Hen Houses were built in Joliet, Illinois, and trucked to the Minnedosa field station for use in Manitoba.

It was there that, in 1991, Delta researchers officially began evaluating Hen Houses as a duck production tool. The concept of the Hen House was simple yet revolutionary: Provide a location where hens could nest over water and above the reach of common predators such as badgers, foxes, and skunks, ensuring a safe nesting environment for the hen and her eggs. The early results were impressive, as more than 50% of the Hen Houses were used by hens within two years and nearly 80% of their nests hatched.

Over the next decade, Delta’s student researchers conducted several studies to determine the most efficient design for Hen Houses. One study determined that landing platforms—used on early Hen Houses in hopes of making them more inviting—were unnecessary and increased costs. Another study showed that using carpet or wicker weave in place of f lax straw cut down on yearly maintenance but also reduced the use rate by mallards. Ultimately, researchers settled on a tubular structure made of woven flax straw supported by a metal frame.

Further refinements to the design and deployment strategies were added through intensive, continual field testing and research projects. But few were as impactful as a Delta study in 2001-2002 by Mississippi State University graduate student Matt Chouinard. His data showed that usage rates and the numbers of hatched ducklings were highest when two Hen Houses were placed on each small wetland while grouping four Hen Houses in close proximity resulted in lower usage rates and less efficient duck production.

Hen Houses have proven to be an exceptionally successful tool to produce ducks, achieving nest success of up to 80% in many areas where they’ve been deployed. A comprehensive study near Delta’s Minnedosa Field Station showed 60% nest success by mallards using a Hen House, compared to less than 3% for ducks nesting in nearby grass cover. This study found that Hen Houses were responsible for most of the yearling hens that returned to nest in the area in subsequent years. In Minnesota, mallards occupying Hen Houses had over 80% nest success, compared to just 13% in the grass. Use rates are generally high, typically climbing to over 60% in most areas. Some areas have even topped a 100% usage rate, as Hen Houses may be occupied by two or more different hens during each nesting season.

“The main reason they work is because of very high nest success, which is a metric that waterfowl managers have been searching to improve for decades,” said Chouinard, who today serves as waterfowl programs director for The Duck Hunters Organization. “Hen Houses probably have the biggest impact on nest success of any program.”

Research has indicated that Hen Houses provide other important benefits to ducks. Hen Houses protect the nesting hen by making it much more difficult for mammalian predators, such as coyotes and foxes, to reach the nest and by providing an overhead barrier to raptors. In addition, the newly hatched ducklings in a Hen House simply drop out of the nest into the relative safety of water, whereas those hatched in a ground nest might have to travel across a treacherous stretch of land to reach water, inviting an opportunistic predator to grab an easy meal.

Shift to Duck Production
When Delta began exploring the concept of Hen Houses (and Predator Management) in the 1990s, the organization’s primary mission was waterfowl research while also educating future waterfowl management leaders. However, Delta’s Duck Production programs held so much promise as tools to make ducks that Delta’s leaders were unable to simply hope that waterfowl managers would come calling to implement them.

Late in 2002, then chairman of the board Dr. Tom Hutchens declared, “Welcome to the new Delta. Today, we are no longer content to be known solely for our research. Our future is now tied not only to the research program and the understanding and solutions it delivers but also to the operation of the waterfowl production tools that are generated through our renowned student program.” Delta Waterfowl had identified, studied, and shone a bright light on a major problem—too many predators on the key duck nesting landscape. And now, Delta was poised to do something about it.

“Delta’s research has shown that we now have simple, practical and cost-effective tools (Hen Houses, along with Predator Management and Habitat Conservation programs) that can increase duck numbers today,” Hutchens wrote in his Chairman’s Message. “We need your help as we try to influence state and federal agencies and conservation organizations. Much needs to be done as we expand with our research program, proceed with our new vision for duck production and continue our battle for the future of waterfowling.”

With his words, Hutchens had proclaimed to the waterfowl management community that Delta was transitioning from primarily a research-focused organization to one that’s equally focused on the business of duck production. Just as important, Hutchens’ message served as a rallying cry for duck hunters to support an organization that was actively working to put ducks over their decoys.

That message, along with Delta’s Hen House program, would ultimately be spread far and wide. A notable moment occurred in 2007, when Chouinard—who had defended his master’s thesis on Hen House research in 2003 and found employment with the U.S. Fish and Wildlife Service—returned to Delta to manage its Hen House program in Minnesota. And as word spread of Delta’s cutting-edge, proven tools to make ducks, the organization grew. Chapters were added. Membership expanded exponentially. Individual major donors started asking questions. And now, nearly 20 years later, thousands more of the mallard-making cylinders are being installed every year, and substantial numbers are available to nesting hens in Alberta, Saskatchewan, Manitoba, North Dakota, Minnesota, and other significant areas where waterfowl breed.

More Hen Houses, More Mallards
In the winter of 2025, Delta added more than 2,100 new Hen Houses across Saskatchewan, Manitoba, Alberta, South Dakota, and North Dakota, bringing its total fleet of nesting structures to more than 14,000—a 17% increase.

“Delta continues to expand our impact for ducks and duck hunters throughout North America,” Chouinard said. “It’s another year of significant growth of Delta’s Hen House program, adding to our record number of nest structures to produce more ducks.”

Delta’s efforts are supported by a growing team of 46 Hen House contractors, who are responsible for installing and maintaining the structures during winter. Additionally, a new Hen House distribution hub has been added in Saskatchewan, and new regional biologists Ryan Kroeger in Canada and Zac Copeland in the United States will help deliver the program.

“We’re growing at a faster pace than we ever have, and with that growth, we’re looking to make our programs more efficient,” Chouinard said. “We’re increasing our capacity to produce ducks. It’s exciting.” Chouinard is especially eager for the potentially monumental impact that Delta’s Million Duck Campaign (MDC) will have on the Hen House program. While MDC has already begun to be delivered, once fully funded and operational, it will result in more than 110,000 Hen Houses welcoming hen mallards each spring across North America’s core breeding grounds.

“MDC ensures that we can continue to add impact to Delta’s programs,” said Joel Brice, Delta’s chief conservation officer. “Our goal is to dramatically scale up delivery of Delta’s Hen House program to produce more ducks and make every fall flight stronger.”

The ambitious goal of the broader MDC—a $250 million fundraising effort— is to add 1 million ducks to every fall flight every year, forever. Hen Houses will play a central role and, based on band-return data, they’ll add mallards to all four flyways.

A Duck Production Revolution
You might say that the evolution of Hen Houses is on the cusp of fueling a revolution in Duck Production history. At full scale, the Million Duck Campaign will continue to drive the program’s growth and new considerations for Hen House designs and strategy. Taken altogether, it makes the goal of putting 1 million “extra” ducks in the air per year a realistic endeavor.

“Hen Houses are a proven efficient and effective way to produce more ducks, and they don’t interfere at all with farming activity,” Brice said. “These are reasons why we feel they’ll be an increasingly utilized and critical tool to make mallards—North America’s most popular duck among hunters—now, next year, and long into the future.”