Do we have too many mallards?

Most hunters, who have seen few ducks and experienced moderate to poor success during the past few seasons, would reply, “What kind of question is that? We have too few mallards.”

Yet this question is being raised in a new Adaptive Harvest analysis that suggests fewer breeding mallards are necessary to maximize the long-term kill – a finding that is sure to spark controversy. The finding is contained in a draft Adaptive Harvest Management report entitled “Reuniting Waterfowl Management.”

According to the analysis, which is being circulated to select individuals for comment, a mallard breeding population of 5.9 million would produce the “maximum sustainable harvest” under average conditions over the long-term. This contrasts sharply with what we have been led to believe over the last century. It also is far below the 8.8 million population goal set by the North American Waterfowl Management Plan.

Last spring’s mallard breeding population (the tally from the traditional North American survey area, plus the states of Minnesota, Wisconsin and Michigan) totaled 8.8 million – significantly fewer ducks than today’s habitat can support. The analysis states that “in the absence of harvest ... the breeding population size would average 11.5 million mallards.”

The conflicting mallard breeding-population data thus breaks down like this:

MALLARD BREEDING POPULATION DATA

abitat Can Support 11.5 million

North American Plan Goal 8.8 million

Adaptive Harvest Optimum Population 5.9 million

This tells us the Adaptive Harvest’s optimum population is 33 percent below the North American Plan goal and 49 percent below what the habitat can support. (This confirms Madduck’s frequent assertion that today we have a large amount of unoccupied breeding habitat and that the gun plays a significant role in determining the size of our breeding population.)

The analysis argues that large numbers of breeders create a duck-production inefficiency that strikes at the heart of Adaptive Harvest’s long-term goal of maximizing the kill. Therefore, we need a lower breeding population to boost production efficiency and allow the Adaptive Harvest model “to maximize long-term cumulative harvest.”

The report declared that if the mallard breeding population averaged 11.5 million, “the sustainable harvest would ... be zero.”

If all of this strikes you as bizarre, rest assured you are in good company. It is contrary to what most waterfowl hunters have experienced over the years, namely that large breeding populations coupled with abundant water on the northern prairies produce the largest fall flights and best hunting.

The analysis comes at a time when revisions are being considered for the North American Waterfowl Management Plan – the guiding document for waterfowl management. The current plan, established in 1986, sets a mallard breeding population goal of 8.2 million under average environmental conditions. (This goal increases to 8.8 million under the Adaptive Harvest model due to the inclusion of Minnesota, Wisconsin and Michigan, three states not included in the traditional North American waterfowl breeding survey.)

But the North American plan conflicts with Adaptive Harvest Management, whose goal is to optimize the kill over the long-term while simultaneously meeting the mallard breeding-population objective. The 8.8 million population goal is too high to “maximize the harvest” because of density dependence, a biological phenomenon reflecting the belief that as the mallard population increases, and the density of ducks on the breeding grounds rises, the per capita juvenile production rate decreases. Adaptive Harvest argues this is a central feature of mallard population dynamics.

“On the continental scale, as the population goes up, we see a decrease in net productivity,” said Mike Runge, the lead author of the analysis. “At half the carrying capacity, you get the most productivity,”

Thus, Adaptive Harvest concludes that while we have sufficient habitat today for 11.5 million mallards (an estimate known in biological terms as the landscape’s “carrying capacity”), and the North American goal is 8.8 million, maintaining breeding populations at either of these levels is inefficient. It requires reducing the harvest to replace surplus breeders that die of natural causes. Therefore, to kill the most mallards over the long-term, the breeding population should be reduced to 5.9 million.

Importantly, Adaptive Harvest does not identify the biological cause for this productivity decline – a key omission.

Runge speculated that it may be related to nesting sites. The number of premier nesting sites, places where a hen is largely assured of hatching a clutch of eggs and fledging a brood, are limited in number. The remaining sites are mostly unproductive, he suggested.

However, he emphasized, “We don’t need to know exactly what the ecological mechanism is” because its existence is revealed in Adaptive Harvest’s crunched numbers.

The analysis further found that if the North American Plan achieved its objective of increasing the amount of breeding habitat on the northern prairies, the carrying capacity would increase to16 million mallards and the most efficient breeding population would increase to “around 8 million.”

Finally, the analysis suggested that reducing the mid-continent mallard breeding population to 5.9 million would provide for an average annual sustainable harvest of 1.35 million mallards – the number that would achieve the maximum kill over the long-term. The 2000-02 average annual mallard kill for the Mississippi and Central Flyways, where most mid-continent greenheads are bagged, totaled 3.9 million.

What are we to make of all this?

The analysis raises several key questions.

– If we assume Adaptive Harvest’s latest analysis is correct (and there is considerable debate about this), do we want drive our breeding stocks downward to maximize the harvest over the long-term?

– Is maximizing the harvest (or its sidekick known as “optimizing the harvest”) a fundamental concept of conservation? Or is it a market hunting ploy reflecting the belief that killing as many ducks as possible will maximize license sales, equipment purchases and donations to purported waterfowl conservation organizations?

– Will hunters be satisfied with seeing scant numbers of ducks in the fall flight, even though this might result in a higher kill over the long-term?

– Is Adaptive Harvest’s latest analysis mostly a “cover your ass” document designed to excuse its failure to produce large numbers of ducks in recent years?

– Is it realistic to assume Adaptive Harvest will actually call for a reduction in the harvest, given its eight-year track record that consists solely of liberal season lengths and bag limits?

– Should North American Plan representatives work more closely with Adaptive Harvest managers to achieve more compatible population and harvest goals?

– Is the effort to maximize the mallard kill, with long seasons and high bag limits, compatible with managing troubled species like the pintail, canvasback, black duck and lesser scaup?

Keep in mind that during the past four seasons many hunters have complained about seeing few ducks. The average breeding population during the years 2000-03 averaged 8.2 million, producing a fall flight that left many hunters staring at empty skies.

Historically, we have experienced our best seasons when high breeding populations are coupled with large numbers of potholes on the northern prairies. Do we want to abandon this goal in favor of an untested mathematical analysis?

This question will be key in the upcoming debate over the future course of waterfowl management. It is important to note that any proposed revisions to the North American Plan or Adaptive Harvest Management will be made behind closed doors. By the time the proposals are released for “public comment,” the odds for reversal or change are minimal. It therefore behooves each of us to enter the debate as quickly as possible if we want to influence the future course of waterfowl management and waterfowl hunting.

(NOTE: We believe the coming debate is so important to the future of wildfowling that we have posted the draft Adaptive Harvest analysis on our website. See Reuniting Waterfowl Management , March10, 2004.)