At the turn of the last century ducks were disappearing from haunts where earlier they had gathered in numbers that defied estimation, prompting sportsmen and conservationists to unite in an effort that resulted in the enactment in 1918 of the Migratory Bird Treaty Act, an agreement between the United States and Canada designed to give legal protection to ducks and preserve our flocks from further diminishment.

Over-shooting was blamed for the disappearance of ducks. This prompted authorities during the first half of the century to focus primarily on ways to reduce the kill. Market hunting was banned, along with the spring shooting of ducks. Certain deadly practices – the use of sinkboxes, baiting, night shooting, tolling dogs and live decoys, for example – were declared illegal. Season lengths and bag limits were imposed, and then gradually reduced. The second half of the century emphasized scientific investigation designed to give us insight into the natural and human factors that affect waterfowl populations. The post-World War II era witnessed the first generation of waterfowl biologists swarming across the North American continent, producing a wealth of population, habitat, production and harvest data.

Yet, a hundred years later, the question remains: Have these efforts – and they are substantial – produced a new wisdom? Has waterfowl management gotten smarter?

Much has changed since those historic days of the early 20^th Century, especially the landscape where ducks nest, gather during migration and spend the winter. But one factor remains the same. Notwithstanding periodic population fluctuations triggered by changing wetland conditions on the breeding grounds, the general belief among today’s old-timers is that over the decades fall flights have become visibly thinner, prompting them to ask the same question their forebears asked a century earlier: “Where are the ducks?”

So, let us examine the biological data, chart the latest trends and see how the lessons of last century are being applied by waterfowl management at the beginning of this century. We begin in 1999, the last year of the 20^th Century, and continue through 2005. We focus on mallards, the species we know most about.

Mallard Breeding Population

1999 2000 2001 2002 2003 2004 2005
Year

Figure 1. The North American mallard breeding population declined from 10.8 million to 6.8 million during the years 1999-2005. This represents a drop of 37 percent. Source: USFWS

As you can see by the descending trend line (the solid line) in Figure 1, spring surveys of the North American breeding grounds have found mallard breeding populations declining significantly since the end of the 20^th Century. No waterfowl conservation organization, advisory group such as a flyway council, state or federal government agency disputes the drop in numbers of breeding mallards. They assert it represents a natural population fluctuation caused by subnormal precipitation on the northern prairies, resulting in a decline in the number of nesting potholes and a drop in the number of fledged juveniles. We can test this assertion by looking at numbers of potholes counted each spring during aerial surveys across the northern prairies.

North American Potholes

1999 2000 2001 2002 2003 2004 2005
Year

Figure 2. Numbers of potholes on the northern prairies have ranged from a high of 6.7 million in 1999 to a low of 2.7 in 2002. The average over the seven-year period is 4.6 million, a total that historically represents nearly average wetland conditions. Source: USFWS

The descending trend line in Figure 2 tells us potholes have declined, but overall remained fairly plentiful during the years 1999-2005. Indeed, the pothole counts over the seven-year span suggest nearly average wetland conditions when compared to long-term data, not the extreme dryness that signifies widespread drought.

The alarms begin ringing when we compare the trend lines of the two data sets. Notice the steep decline of the mallard breeding population trend line, compared to the pothole trend line. This tells us mallards are declining at a faster rate than potholes, which raises cause for concern.

Some biologists dismiss this comparison, declaring there is more to reproductive success than numbers of potholes. Historically, they note, fewer potholes result in fewer juveniles being fledged, adding this relationship has worsened in recent times by the loss of upland nesting cover and increased predator populations, a combination that has reduced nest success to levels below the historical norm, resulting in fewer young per breeding hen being fledged today than in year’s past. They argue lower productivity is a primary factor contributing to this century’s breeding population decline.

We can test this assertion by looking at mallard age-ratios, the number of juveniles per adult in the hunter’s bag, waterfowl biology’s traditional measure of reproductive success.

Juveniles per Adult

1999 2000 2001 2002 2003 2004 2005
Year

Figure 3. The number of juveniles per adult in the hunter’s bag, a measure of reproductive success, has nearly doubled for mallards during the first years of this century, increasing from .88 in 1999 to 1.62 in 2005. Source: USFWS

As you can seen by the trend line in Figure 3, mallard juvenile productivity in the early years of this century has been steadily rising, exposing the fallacy that declining reproductive success is responsible for the sharp drop in the North American mallard breeding population.

A related issue involves the fall flight. If reproductive success is increasing, why aren’t hunters seeing more mallards each autumn? The answer to this question involves the relative nature of the mathematical relationship between declining breeding populations and increasing juvenile productivity.¹

For our purposes, we can construct a back-of-the-envelope mallard fall-flight estimate by using the breeding population, adjusted for summer mortality, and the age-ratio, adjusted for juvenile gunning vulnerability, to give us a relative comparison of the fall flights from 1999-2005.²

Mallard Fall Flight

1999 2000 2001 2002 2003 2004 2005
Year

Figure 4. Despite increases in juvenile productivity rates, mallard fall-flights have shown a small, but gradual decline during the years 1999-2005, confirming the observations of many veteran waterfowl hunters.

As you can see by the trend line in Figure 4, mallard fall flights have shown a small but steady decline. This tells us the increase in juvenile production rates is insufficient to offset the loss in numbers of breeding mallards, resulting in fewer ducks flying southward.

A related issue involves the fundamental law of population biology. It states that if deaths exceed births, the population will decline. If births exceed deaths, the population will increase. We know more ducks fly south each autumn than are counted on the breeding grounds the following spring. This tells us the number of ducks lost each year must exceed the number of juveniles fledged, and that the breeding population decline can be attributed primarily to losses during the autumn/winter/spring time period.

We can calculate a back-of-the-envelope over-winter mortality rate by (a) subtracting from the fall flight estimate the number of mallards found on the breeding grounds the following spring, and (b) dividing this number by the fall-flight.

¹ For those of you who are not mathematically inclined, the relative nature of the problem can be easily understood by using the example of a savings account. A three percent annual return on a $1,000 savings account will produce $30 at the end of the year and a total net worth of $1,030. If $300 is withdrawn and the deposit reduced the following year to $700, but the interest rate increased to five percent, interest income will increase to $35, but the $735 total net worth will remain less than the preceding year. In this example, the interest rate would have to increase to 47.2 percent to make up for the withdrawal and achieve at year’s end a total net worth of $1,030. ² The equation: Fall Flight = (Breeding Population x .9) x (1 + Age-Ratio/1.25).

Over-Winter Mortality Rate

1999 2000 2001 2002 2003 2004 2005
Year

Figure 5. The early years of this century find mallards dying at an increasing rate from the time they leave the breeding grounds until they return in the spring, as illustrated by the ascending red trend line. This results in a decline in the number of mallards found each spring on the breeding grounds.

The ascending trend line in Figure 5 tells us over-winter mortality rates have been steadily rising. This brings us to the key issue: What could cause increasing over-winter mortality and prevent mallards from maintaining or increasing their breeding population? Is it a result of natural causes such as disease, predation, starvation or accidental mishaps such as ducks colliding with power lines or being mortally conked on the head by falling hailstones? I am unaware of any biological reports suggesting any of the above mortality factors, acting singly or in tandem, are increasing in lethality and therefore responsible for rising over-winter death rates.

What about the gun? We can test this issue by examining the kill-per-breeding mallard. This is the harvest estimate (from HIP data), adjusted for crippling losses, divided by mallard breeding population.

Kill per Breeding Mallard

1999 2000 2001 2002 2003 2004 2005
Year

Figure 6. The mallard kill rate gradually increased during the years 1999-2005, as shown by the ascending trend line, raising concerns the sport harvest is causing a decline in mallard the breeding population.

As you can see by the ascending trend line in Figure 6, the sport kill per breeder is over-winter mortality and the resulting decline of our mallard stocks during a time of average prairie water conditions and rising juvenile productivity.

One hundred years after early sportsmen and conservationists became alarmed over dwindling numbers of ducks and sought to do something about it, the biological evidence raises the question: Have we regressed, increasing the kill rate by substituting spinning-wing decoys, early seasons, late seasons, longer seasons, split seasons, special seasons, zoning, large bag limits and increasing commercialism for the deadly efficiency of sinkboxes, baiting, night shooting, spring shooting, live decoys, tolling dogs and market gunning, the banning of which once was and still is viewed as the foundation of waterfowl conservation? Have we closed our eyes to modern-day changes that increase killing efficiency in order to maximize each season’s duck kill, the avowed goal of Adaptive Harvest Management? Have we ignored reality by sweeping the telling biological data and anecdotal evidence under the rug?

Have the men and women who currently occupy the upper echelons of our waterfowl conservation organizations, state fish and game agencies, and the U.S. Fish and Wildlife Service learned anything from a century of failed waterfowl management? The scientific evidence suggests they have not. The founding wisdom that our conservation forebears brought to the table and emphasized at the beginning of the 20th Century, that too many ducks are dying by the gun, has eluded today’s waterfowl management establishment, like a wary mallard that refuses to commit to the decoys. The ducks are paying the price and 21^st Century waterfowl conservation has become an empty promise, a chimera that only fools the gullible.

You might want to think about this while sitting in your blind this autumn and winter staring at empty skies.