What, if anything, do waterfowl breeding-ground surveys tell us?

Many hunters scoff at the annual population counts, asserting they either (a) undercount the number of ducks, as in the case of pintails, or (b) over-estimate the number of ducks, as with mallards whose thin fall-flights in recent years have been less than anticipated.

No one can state with precision the number of any North American species. But since 1955 waterfowl management has been reasonably confident that its annual breeding-ground surveys have tracked trends in the size of the continental duck population.

This survey is based on an aerial count of breeding pairs of 10 species of duck populations along a route that stretches across the prairies of the United States and Canada and covers key breeding habitats north to Alaska. It covers the habitats and geographic regions that produce 70% to 80% of the species most sought by hunters.

However it isn’t the total population (which allows biologists to estimate the number of breeding females) alone that determines the size of the autumn flight.

Habitat conditions are very important and these conditions can be highly variable from year to year, especially on the prairies where naturally occurring wet and dry cycles are inevitable. There are many requirements for reproductive success. Nesting cover may be adequate, but without adequate brood-rearing water and the food it contains nesting hens will fledge few juveniles.

To estimate probable breeding success biologists count spring wetlands that are suitable for breeding. These wetlands are again surveyed later in the season to determine if water remains. The assumption is that when water remains, most females will have been successful in fledging at least some of their young. Researchers know approximately how many young females fledge under various habitat conditions, so they can estimate an overall rate of juveniles production. But one must use these figures with caution.

Thus, while the breeding-ground surveys provide useful trend information that is a necessary tool in managing ducks, too often this information has been used to fine tune regulations well beyond the crude nature of the data.

The late John Lynch, one of the original survey biologists and a very experienced “duck man,” proposed a common sense way of setting hunting regulations based on the concept of traffic lights. He used the critical link between prairie water and breeding success to recommend that regulations should be liberal when the prairie is wet (a green light year), conservative when it’s dry (a red light), and somewhere in between during average water years (amber light).

Even today some biologists suggest the breeding-ground survey will never be reliable enough to be more precise.

But Lynch’s compelling proposal never received the attention it deserved. This is partly because some influential professionals view waterfowl management as a more precise science than it is. They view Lynch’s proposal as overly simplistic, perhaps even insulting.

A second factor involves a concerted effort to provide the maximum possible harvest, which has long been in vogue by those setting regulations. I suspect Lynch’s sense of caution would be quite different than theirs.

One legitimate concern about Lynch’s proposal is that water is not the only factor responsible for good duck production. Nesting cover and other habitat conditions have generally deteriorated since Lynch’s day, especially on the Canadian prairie. In general, prairie breeding habitat doesn’t produce the ducks it once did, regardless of water conditions.

There also is a risk in the practice of reporting precise figures for the fall flight forecasts. Too many hunters are unfamiliar with how these figures are derived and believe the estimates represents a precise prediction. They have little understanding of how tenuous the estimates are and mistakenly assume that management has far more “control” over duck populations than it has.

A look at a few of the basic biological assumptions behind the surveys will reveal the inherent difficulty in calculating these estimates.

The first is that what is happening to prairie habitats and to prairie mallards is an indication of what is happening to all ducks in all habitats across the continent. For example, the traditional breeding-ground survey ignores black ducks in eastern habitats. Since the 1980s additional surveys have been conducted to address this concern, but these surveys are even more tenuous than the traditional survey.

A case can be made for using the mallard as an indicator of what is happening with ducks in general. Historically, it has been the most ubiquitous and numerous duck, and one available to more hunters than any other. It also lends itself to being surveyed. The brightly colored male is conspicuous, even from a low flying plane of the kind used in the survey. Furthermore, males are territorial for a 2-3 week period while their females are laying eggs. This means that the otherwise highly mobile male is predictably at home.

If the survey is timed right, the breeding population can be surveyed reasonably accurately.

But other species are very difficult to survey. Due to their behavior, color, lack of visibility in their habitats, etc, species such as green-winged teal, black ducks, goldeneyes and scaup, for example, are especially difficult. These species have been of concern to managers and hunters alike, but we have little knowledge of how many pairs breed each year.

It is even more difficult to estimate each year’s reproductive success. Females and their broods are highly mobile and frequently in dense cover. Trying to count them is almost impossible and attempting to do so can result in misleading information. Instead, it is assumed that the quality of the habitat provides an indicator of reproductive success. Wetlands hosting a breeding pair in May that are still wet in late June, when broods are ready to fledge, are assumed to have produced ducklings. Thus, the estimated number of breeding pairs and the quality of the breeding habitat, with adjustments for weather conditions, provide an estimate of overall recruitment. This allows managers to estimate the size of the fall flight.

There also is concern that the survey has been distorted by changes since 1955. Into the mid-1960s, surveys generally were conducted by the same individuals. While they took the surveys seriously, there was a certain casualness involved. Since then, many more individuals have been involved. Since the 1980s those conducting the survey have been looking harder than ever before for ducks. This was never more so than when water came back to the prairies in the early 1990s and the new millennium was approaching. Managers wanted desperately to reach the North American Waterfowl Management Plans continental goal of 100 million ducks. While it achieved its objectives on paper, many experienced hunters and field biologists had their doubts about the reported record flight.

Another significant change involves adjustments and changes to survey routes.. Indeed, complex statistical analyses have been required to compare annual estimates since 1955. All of this raises the question of whether management is putting too much faith in its survey data. Since estimating duck populations is at best an imprecise science. this alone should make managers cautious about how the data are interpreted.

To be fair, estimating the size of the continental fall flight is an enormous challenge. And if cautiously interpreted, the estimates can provide a reasonable basis for allocating the harvest and setting regulations along the flyways. It is the best survey of waterfowl anywhere in the world, a laudable achievement for North American waterfowl management. Europe has nothing comparable and, except for some goose populations, biologists only the vaguest notion of the size of the fall flights.

The difficulty with our system is that too frequently caution is tossed to the wind. Those who would be cautious are a minority, certainly much less influential than those who espouse the maximum kill philosophy, as evidenced by the current liberal regulations during a time of widespread prairie drought, poor reproduction and grave uncertainty about how hunting mortality will impact the future of beleaguered species like pintails and scaup.

Predictions of large fall flights during the late 1990s played into the greed of many who argued that good times were here again, so why not have longer seasons and more generous limits? The concern of experienced hunters and many wildlife professionals was that ducks never recovered to the extent our surveys and estimates suggested. Could it be, they wondered, that liberal regulations were keeping some duck populations from taking advantage of good quality habitat to increase in abundance?.