Hard Luck Ducks
November 03, 2010
The pintail faces a special set of problems
Residents of the northern prairie get used to strange weather or they get out. This is the region that spawned the old homily, "If you don't like the weather, just wait five minutes." But even by the standards of the upper Midwest, last spring was squirrelly. Last April and May, Cedar Rapids, Iowa, got nearly 11 inches of rain, seven inches more than average, which set the stage for the 500-year flood on the Cedar River in mid-June. Up in Bismarck, a dry winter led into a drier spring-- in April and May, about two inches of rain fell, half the normal. The weather in Saskatchewan and Alberta was about the same--not a Dust Bowl but substantially drier than last year.
The result was predictable. Many of the basins that held water last spring were dry this spring. The traditional May pond count was down 37-percent from last year and 11-percent from the long-term average. It's interesting and more than a little puzzling to consider the way different duck species responded to the change.
And, once again, pintails took it right in the tail feathers. Estimates of sprig breeding populations are off 22-percent from 2007, 36-percent below the long-term average. Since the 1970s, pintails have consistently been at the bottom of the statistical heap. When there's a good year, pintails don't respond as vigorously as other puddle ducks; when there's a drought, they fail more spectacularly. The effort to get to the bottom of the pintail's troubles has intensified as the bird's population has declined, and the researchers are finding a number of issues that may be contributing to the overall malaise.
Information from the 2008 aerial surveys reflects one behavioral peculiarity that may be causing problems. The only rise in pintail numbers occurred in Alaska, the Yukon, and the boreal forest from northern British Columbia into the Northwest Territories, suggesting that a fair number of pintails took one look at the drought in the prairies and kept on flying to join the segment of the pintail clan that nests in the north country every year. According to the late Frank Bellrose, pintails are the most common dabbling duck in the Arctic, but pintail numbers in the north are particularly high when the potholes are dry.
Other ducks share the habitat of over-flying the potholes in times of drought, but no other species does it more often or goes farther north than the pintail. The obvious advantage to the Arctic is that a hen is likely to find more extensive nesting cover and brood-rearing areas in the northern boreal forest and tundra than on the drought-stricken prairie--the disadvantage is that she has to burn a lot of her energy reserves just getting there, leaving less for the business of egg production and incubation.
Hens that fly on north tend to produce smaller clutches and, if their first nests are destroyed, they're less likely to renest. If they're sufficiently stressed by the migration, they may not bother to lay eggs at all. A drought year in the prairie, then, is likely to lead to lower production among pintails.
Researchers with the U.S. Fish and Wildlife Service have calculated how far north pintails generally travel before nesting. Their analysis shows that, beginning in the mid-1970s, the center of pintail nesting began to shift north. On average, pintails are now nesting three degrees closer to the North Pole than they did in the 1970s. The birds may be reacting to the deterioration of upland cover in the prairies, even when there is plenty of water, or the prairie-nesting component of the population may be dying out because of low breeding success. Either way, more pintail hens are traveling farther north these days and producing fewer ducklings as a result.
Biologists working in the playa lakes of the Texas panhandle measured fat deposits and body condition of pintails wintering in the area in 2002 and 2003, then compared them with similar measurements taken from birds in 1984 and 1985. Over that 20-year span, fat in adult males declined by 18-percent; in adult females, it dropped by 39-percent.
Farther east in the lower Mississippi River valley, changes in rice agriculture may be reducing the amount of food for pintails and other waterfowl. New varieties of rice developed in the 1980s allow farmers to plant and harvest their grain earlier. After harvest, they flood the rice fields to break down the rice straw more rapidly. Unfortunately, this also gives waste rice the chance to break down or sprout before the ducks arrive. One researcher has estimated that the change has resulted in a 79-percent loss in waste rice by early December.
Then there is the ongoing deterioration of the huge wetland complex along the Gulf Coast of Louisiana and Texas, one of the major traditional wintering grounds of the continent's pintails. Over the last century, these marshes have been cut off from the silt-laden waters of the Mississippi, and without the constant addition of muck, they have slowly subsided, yielding steadily to the wave action of the sea. Navigation channels, pipeline corridors, and other human activities that open stands of marsh vegetation to salt water have accelerated the process of wetland destruction.
Three summers ago, I had a chance to fly over the coastal marshes south of Lake Charles, Louisiana, nine months after Hurricane Rita, a category five storm, came on shore. We covered 10 miles of the coast at an altitude of about 500 feet, and the shallows below were one gigantic debris field with an occasional house roof or chest freezer recognizable in the wreakage. Not the sort of place a hen pintail can use to fatten up for the spring migration to the prairies, let alone the Arctic.
This fundamental problem of fuel haunts another duck species, the lesser scaup. Scaup and pintails have almost nothing in common. The pintail is a dabbler; the scaup is a diver. Through most of the year, the pintail is a seed eater that picks up an occasional clam or insect; the scaup eats snails and other invertebrates with a little vegetable matter on the side. The pintail is one of the earliest arrivals on the spring nesting grounds; the scaup is one of the latest.
But the two species have a couple of things in common--the core of their winter range is along the Gulf Coast, and they nest in the river deltas and tundra of the Far North. This shared taste for northern nurseries puts pressure on both species to lay eggs and raise young as quickly as they can, which means that the hens of both species need to arrive on their nesting grounds with significant fat reserves. In the last 30 years, both pintails and scaup have struggled to accomplish this. The reasons for the spring food shortages are different for the two species, but the effect is the same-- over the last 30 years, both have shown almost identical declines.
Pintails that breed in the pothole country have one last problem. They like to nest in thin cover. Back when the only men on the prairies wore eagle feathers in their hair, this was probably a successful strategy. Pintail hens spread out over millions of acres of mixed and shortgrass prairie, often far from the wetlands that attracted other duck species and ju
st as far from the predators that hunted eggs and ducks around those marshes.
But that wilderness of grass has given way to the plow. These days, the prairie is broken up into smaller and smaller pieces, surrounded by relatively barren cropland. Predators concentrate on these skimpy patches of grass, where a pintail nest is hard to hide. Studies in the Dakotas have shown that the red fox is the main killer of nesting pintail hens; other research in the Dakota and southern Canada suggest that the primary culprits are raptors. Either way, losses are high.
The impact of predators is compounded by farming practices. For decades, grain stubble left through the winter has exerted a powerful attraction on pintail hens. Unfortunately, their nests often don't hatch before farmers plow these stubble fields, and many of the clutches there are destroyed.
Nearly everything we've done over the last 50 years, from the prairie parklands of Canada to the Mississippi delta, has been bad for pintails. Evolutionary strategies that have served the birds well for thousands of years on some of the world's most challenging landscapes are suddenly liabilities. They're an adaptable breed, born and bred in some of the most unpredictable landscapes on earth. I think they'll pull through.
But they could sure use some help.