By Jim Ringelman, Ph.D., and Bruce Batt, Ph.D.
Like many scientific disciplines, waterfowl management began with casual observations and trial-and-error experimentation. Over time, managers developed paradigms—commonly held beliefs about how waterfowl responded to our management actions. Often, further study reaffirmed the validity of these paradigms, and they became foundational to waterfowl conservation. But every once in a while, paradigms shift unexpectedly when nature throws us a curve or research uncovers new information that challenges conventional wisdom. Some of the most interesting paradigm shifts have occurred with the management of prairie-nesting ducks.
To increase waterfowl populations, one has to increase either survival or reproductive rates. Early paradigms in waterfowl management addressed both, but the effect of hunting on ducks was the first to come under intense scrutiny. Before the abolishment of market hunting, unregulated harvests were causing many duck species to decline. Given this experience, concerns about the effect of sport hunting on duck populations continued even after market hunting ceased. Then, in 1976, waterfowl researchers had a breakthrough. Using mallard banding data and new analytical approaches, a new paradigm emerged: mortality from hunting was, at least in part, compensatory with natural mortality, much of which occurred on the breeding grounds. In other words, some portion of mallards shot by hunters were going to die from natural causes anyway, so hunting mortality should not be thought of as completely additive to mortality from other causes. This new paradigm fundamentally changed the way biologists viewed hunting mortality in ducks, and continues to guide contemporary waterfowl hunting regulations.
In the 1930s, less than two decades after market hunting was abolished, waterfowl conservationists faced another challenge. Severe drought, compounded by widespread wetland drainage, had overtaken the Prairie Pothole Region (PPR) vital to breeding ducks. Duck populations were plummeting, and to reverse the trend wetlands would need to be restored on a massive scale. This crisis resulted in the creation of the federal duck stamp and the founding of Ducks Unlimited, both of which were dedicated to raising funds for wetland restoration work. In the fall, when many waterfowl enthusiasts were in the field, ducks were most numerous on large wetlands. Thus it was assumed that these were the most important wetlands for waterfowl, and they became the focus of restoration work. Mindful of periodic droughts that were the norm in the PPR, efforts were made to permanently restore wetlands by increasing their capacity to hold water or providing a supplemental water source. The new paradigm was to "drought-proof" large prairie wetlands to save the ducks.
As this paradigm was gaining traction, waterfowl research became more extensive and sophisticated. Biologists examined the foods consumed by ducks during the spring, and found that nesting hens ate large quantities of aquatic invertebrates, which contain the protein and calcium needed for egg production. These invertebrates were most abundant in small, shallow wetlands, as opposed to the larger wetlands that were receiving the greatest attention at the time. Biologists also observed territoriality among breeding ducks, a behavior that causes birds to isolate themselves within a community of small wetlands. As these and other findings began to emerge in the scientific literature, the paradigm of what constitutes important breeding habitat began to shift. It became increasingly apparent that communities of small wetlands were vitally important for breeding ducks. These revelations caused conservationists to focus on the protection and restoration of small wetlands, a practice that continues today.
Many duck populations rebounded nicely in the 1970s, and it appeared that efforts to conserve small wetlands were paying off. But that sense of optimism changed during the 1980s, when drought again gripped the prairies and scientists tallied the massive loss of wetlands and grasslands that occurred during the previous decade. Even more foreboding was new research that revealed mallard nesting success was an abysmal 8 percent on agricultural landscapes in North Dakota, which was thought to be representative of other cropland-dominated areas of the PPR. Population models predicted that duck numbers could not be sustained under such conditions. Breeding ground surveys supported the prediction, as prairie duck populations declined 33 percent from 1979 to 1985. The new paradigm concluded that extensive grassland loss was concentrating nesting birds in the remaining fragments of upland habitat, and the focus turned toward efforts to increase nesting success.
One solution adopted by some managers was to trap and kill predators. However, most biologists were aware that this would be a never-ending task, because after one predator is removed another moves in to take its place. It was thought that more enduring solutions would involve the creation of managed habitat that would allow ducks to nest in predator-free environments. Researchers began examining nesting success in dense nesting cover, on islands, in elevated nesting structures, within fenced exclosures, and in other situations that would minimize mammalian predation. Their findings looked promising, and so began a period of intensive management that saw the installation of thousands of nesting structures, the construction of hundreds of nesting islands and fenced enclosures, and (if one includes the Conservation Reserve Program) the planting of millions of acres of dense nesting cover.
Regrettably, over time it became apparent that these intensive management practices were less effective than anticipated. Predator control increased nesting success, but it did not necessarily result in a comparable increase in fledged ducklings. Predators invaded nesting islands during the winter and during periods of low water, and had to be removed every spring. Fenced exclosures impeded hens and broods as they traveled from their nests to water, resulting in duckling mortality. Across the board, operation and maintenance of these practices was an increasingly costly annual expenditure.
As all this was unfolding, the ducks surprised us again. The PPR became very wet in the mid-1990s, and breeding duck numbers skyrocketed more than 70 percent. During the past decade, there was another boom that further boosted some species to all-time highs. Conservationists began to realize that their previous efforts, coupled with existing grasslands and wetlands, were enough to fuel "duck booms" when wet conditions prevailed. However, those wetlands and grasslands continue to be lost at an alarming rate. This resulted in the paradigm that prevails today among most conservation organizations. Simply stated, while there is a time and place for intensive management and habitat restoration, the priority within the PPR is to maintain the existing grasslands and wetlands to "keep the table set" for duck booms when favorable water conditions exist. Using perpetual wetland and grassland easements and outright fee purchases, these habitats are being secured forever with a onetime payment to private landowners. Other initiatives conducted in concert with the agricultural community encourage practices that sustain waterfowl production on farmed landscapes.
Adopting new paradigms is not easy for any organization or individual, but it is crucial to keep an open mind and to rely on scientific information that enables us to make objective, informed decisions. A continued investment in science will ensure that our conservation efforts are focused on activities and landscapes that are most important to continental waterfowl populations. History has shown that this approach has served waterfowl conservation well for the past 100 years, and it should continue to do so in the future.
Prior to their retirement, Dr. Jim Ringelman and Dr. Bruce Batt helped lead DU's conservation work on the prairies for many years. Ringelman served as director of conservation programs in DU's Great Plains Region, and Batt was the organization's chief biologist.