Math is the language of science. This is as true for duck science as it is for astrophysics. But waterfowl biology’s cryptic equations, designed to offer scientific
“proof,” often are opaque to the layman. What can easily understood, back-of-the-envelope calculations tell us as we seek to increase the fall flight? Plenty.

Spinning-Wing Decoys: The U.S. Fish and Wildlife Service’s recently issued paper, “Review of Electronic-Motorized Decoys For Taking Migratory Game Birds,” tells us:

• “The percentage of hunters using some form of these devices has increased steadily since 1999 (now exceeding 50 percent in many areas).
• “Overall, about 70 percent of all ducks harvested in (spinning-wing decoy) studies were taken while using SWDs, while approximately 30 percent were harvested when the SWDs were not in use.”

What do we discover if we assume half of all American hunters use spinners, these hunters kill half of all ducks and spinners account for 40 percent of their kill?

In 2003, the last year for which U.S. Fish and Wildlife Service harvest data is available, hunters retrieved 13.4 million ducks. Hunters with spinners therefore killed 6.7
million ducks. Spinners accounted for 40 percent of this kill – a total of 2.7 million ducks.

To put this figure into perspective, you should note that all national wildlife refuges and waterfowl production areas annually produce an estimated two million ducks. The
multi-billion dollar Conservation Reserve Program (CRP), which has restored millions of acres of cropland to grassland in the Dakotas and eastern Montana, produces an estimated 2.2 million additional ducks each year.

Spinners, therefore, are responsible for killing more ducks than are raised on all national wildlife refuges or produced by CRP. The “spinner kill” also exceeds the number of ducks biologists estimate are raised on all Ducks Unlimited projects.

Interestingly, spent lead shot was blamed for killing an estimated two million ducks each year, 26 percent less than are taken by the use of spinners. This was considered a bad thing.

We banned lead shot. Should we do the same for spinning-wing decoys?

Egg Math: Robert McLandress wears two hats. He has a Ph.D. in waterfowl biology. He is president of the California Waterfowl Association. When he speaks, he speaks with the authority of a biologist (who presumably knows something about ducks) and president of an organization (with a political agenda).

In his bi-monthly column he recently sought to minimize the impact of hunting on declining breeding populations by saying that “only a tiny amount (less than three percent) of all the eggs laid by ducks in spring each year end up as ducks in the hunter’s bag.”

It this curious statistic true?

We can conduct a back-of-the-envelope test by looking at California mallards, a local population that provides on average two-thirds of the mallards California hunters
bring to bag. We will look at the year 2003, the last year for which all data is available.

U.S. Fish and Wildlife Service harvest data tells us that in 2003 California hunters bagged 288,094 mallards. Assuming 67 percent were raised locally, this means 193,023
resident mallards ended up in the bag. Age-ratio data further tells us 71 percent were juveniles. Thus, the local juvenile kill totaled 137,046 mallards.

If these ducks constituted three percent of all eggs laid that spring, then California’s hens laid 4.6 million eggs. Note that this total is minimal. It excludes juveniles that survived the season or were crippled and avoided retrieval.

California’s surveyed 2003 hen mallard breeding population totaled 161,808, assuming a 52:48 male-female population ratio. This means each mallard hen laid on
average 28.4 eggs. Assuming nine eggs per clutch, this works out to 3.2 nesting attempts per hen.

Is this likely? No. Although some hens do not nest, some nest once, some nest twice, a few nest three times and so on, the average is believed less than 2 attempts per hen.

Interestingly, other mathematical tests also failed to confirm McLandress’ estimate. Moreover, we asked other authorities to confirm the three percent figure. None could.

Thus, the figure’s accuracy appears doubtful.

This raises the question: If we are to make biologically based decisions on the management of waterfowl, shouldn’t we demand more realistic data from our conservation organization spokesmen, especially those with a biological background?

Adaptive Harvest Management: The technical committees of all flyways have expressed opposition to major elements of regulatory changes proposed by an Adaptive Harvest Task Force sponsored by the International Association of Fish and Game Agencies.

The proposed changes include reducing the four current regulatory options (liberal, moderate, restrictive and closed seasons) to three (standard, conservative and closed), and reducing the daily bag limit. The technical committee’s opposition to some changes (including elimination of the liberal season alternative) does not necessarily foreclose enactment of the proposals. Other groups also must give their opinion before the U.S. Fish and Wildlife Service enacts the regulations for the upcoming season.

We will keep you posted on any proposed changes if they occur.

The hunting regulation changes proposed by the Task Force, compared to the current “liberal” option, are:

ATLANTIC and MISSISSIPPI FLYWAYS

CENTRAL FLYWAY

Low Plains

High Plains

PACIFIC FLYWAY

Note: The “Standard” framework would allow for the continuation of season extensions, i.e. late September opener and Jan. 31 closure. The “Restrictive” model’s framework dates run from the Saturday closest to Oct. 1 to Jan. 20.

To read the complete Task Force report, go to the US Fish & Wildlife Service site.