Of all ducks that wing the length of the North American continent, none is more troubled than the pintail. For more than half a century its flocks have steadily declined. Breeding-ground surveys record the pintail’s alarming descent.

Figure 1. The North American pintail breeding population has declined 83 percent from its 1956 peak of 10.4 million. Fewer than 1.8 million pintails were counted in the 2002 spring survey. Source: USFWS.

In recent years authorities have blamed “habitat” for the pintail’s population decline. They cite the loss of native prairie grasses and the pintail’s affinity for nesting in grain stubble where clutches often are destroyed during spring plowing and seed-drilling operations.

But in the Dakotas and eastern Montana the government-subsidized Conservation Reserve Program resulted in the conversion of 4.7 million acres of cropland to grassland.

The years 1979 and 1999 provide a graphic comparison. In the pre-CRP year of 1979 biologists counted 1.5 million potholes in the region. Two decades later biologists

counted the same numbers of potholes, but the region bloomed with lush CRP grasslands that provided new, high quality, upland nesting habitat. Yet the hen pintail breeding population in the three-state region fell from 516,000 to 365,000 – a 29 percent decline over two decades.

Nest predation has been another cause of concern. In recent years authorities have blamed increasing prairie nest predation for diminishing fall-flights. But a look at hen pintail age-ratios over the past quarter-century reveals the number of juveniles per adult has gradually increased while its breeding population has declined. This sharply contrasts with the mallard, whose age-ratios have decreased while its population has remained stable or increased.

Thus, as we showed in Part II, agriculture and predation cannot account for all the losses.

Another problem involves disease. In wet years botulism losses on the northern prairies can be horrendous. These die-offs can take an extraordinary large but unquantified toll.

This leaves hunting as the only remaining significant form of mortality. A look at the kill since 1961, the first year of harvest surveys, shows a steady drop in the kill since 1970, as you can see in the following graph.

Figure 2. The U.S. pintail killed has ranged from a peak of 1.9 million in 1970 to a low of 209,884 in 1988. During the recent wet years from 1994-99 the annual kill averaged 528,667. Source: USFWS.

Traditionally, authorities have discounted hunting as contributing to the pintail’s long-term decline, a conclusion based largely on questionable band-data analysis. But this fails to explain the U.S. Fish and Wildlife Service’s bizarre regulatory record over the past quarter-century.

In 1975, biologists counted 5.9 million pintails across the North American breeding grounds, compared to the peak 1956 population of 10.4 million birds. Yet this stark 43 percent drop failed to prevent the U.S. Fish and Wildlife Service that year from increasing the daily pintail bag limit in the Atlantic, Mississippi and Central Flyways to 10 daily, compared to four or five in previous years.

Why, you might ask, did the service seek to increase the kill after the pintail’s population had plummeted? The answer is shrouded in deep mystery. The most frequently heard explanation suggested that it was engineered by an influential Ducks Unlimited officer.

I have seen only one written document pointing to this individual, even though in the 1980s I searched the files under a Freedom of Information Act request. The service’s failure to adequately explain its action suggests the agency compromised its professional integrity and has ever since engaged in a cover-up.

The 10-a-day bag continued for the next decade. When it ended in 1985 the continental pintail breeding population had fallen to 2.5 million, a 76 percent drop from the species’ peak. It forced the service to impose a one-bird per day bag limit.

In 1997 a slight bump upward in the pintail’s breeding stocks once again caused the service to take leave of its senses. It increased the nationwide daily bag limit to three and added 10 or more days to the regular season, both of which would contribute to an increased kill.

At the time I was living in Maryland on the shores of Chesapeake Bay, the cradle of American wildfowling. Surveys revealed that from 1955 to 1997 the state’s wintering pintail population had dropped from 55,964 to 1,805 – a 95 percent decline in my lifetime. This prompted me to call the state’s waterfowl biologist.

“How do you biologically justify an increased kill when the population has declined 95 percent?” I asked.

The Maryland situation was somewhat different from states in the other three flyways. That year a number of Atlantic Flyway states were allowed additional hunting days to compensate for traditional prohibitions on Sunday hunting. Thus, in previous years the actual number of hunting days in a 50-day season might total only 43 days. The compensatory days, when coupled with the liberalization that extended the season length from 50 to 60 days, meant that Maryland received a 40 percent increase in season length, coupled with an increase in the daily bag limit from one to two.

This theoretically meant a Maryland waterfowler who killed his pintail limit each day throughout the season could increase his seasonal kill from 43 to 120 pintails – a 130 percent increase.

The state biologist was somewhat taken aback. He had not examined historical winter survey numbers. He sought to fend off criticism by suggesting the loss of aquatic grasses in the bay had caused pintails “to winter elsewhere in the flyway.”

“The flyway population has declined 90 percent,” I replied. “There is no elsewhere.”

“Well,” he continued, “we don’t know that much about the pintail population in the Hudson Bay lowlands.”

I pointed out this suggested ignorance was a valid reason to increase the kill of a declining species – a rationale that undermines the justification for scientific investigation and runs counter to what we know about duck survival.

He then weakly responded that the state only increased the bag limit from one to two -- instead of the three-daily maximum allowed under federal law – as if this excused the state’s reprehensible action.

The exchange posed a key question. As I asked him, “At what point do we impose a pintail-hunting moratorium to allow the species to recover – when the population declines to 97, 98 or 99 percent?”

Pintails are more imperiled in the Atlantic Flyway than in any other region of the country.

For the 2002-03 season, authorities sought to reduce the kill by reducing the season-length in all flyways, effectively creating a “season within a season” in an effort to reduce the kill. It followed analyses suggesting the sport kill has blocked efforts to rebuild our flocks.

For example, the allowable harvest for the 2001-02 season in the Mississippi Flyway called for a maximum kill of 19,000 pintails. The estimated harvest totaled 129,000 – more than six times greater than desired.

How much of an effect these new restrictive seasons will have remains to be seen.

The pintail’s problems continue.

We have in these first three parts explored the various factors that have been cited over the years as factors in the pintail’s decline – habitat loss, agriculture, predation, disease, over-shooting and management incompetence. How do we determine degrees of culpability for each suspected factor? How do we plot a course for recovery?

The answer lies in the development of a population model, a mathematical accounting of births and deaths that is the biological equivalent of a financial income and expense statement.

We will, therefore, crunch the numbers and develop a population model in the final installment in an effort to create a recovery plan..

Next: Part IV -- A Pintail Population Model.