The Snow Geese of the Central Flyway
Walking down the hall of our university’s biology building on a winter day during the late 1990s, I overheard two young men recounting their recent activities. One was proudly telling the other that he and some friends had killed over 120 “sky carp” the previous Saturday. Initially I had no notion of what he was talking about, but it soon became apparent that he was talking about snow geese and that he had exploited newly relaxed regulations that permitted winter snow goose hunting with few limits on the number of birds that could be shot in a day. I could scarcely imagine why anybody could take pleasure in killing that many geese, much less brag about it. Since childhood, snow geese have been my symbol of unmatched beauty and grace in the natural world.
On my birding trips to the Platte Valley later that spring and during following ones, I came to see all too clearly the effects of spring hunting on the behavior of both snow geese and other waterfowl. All the birds had abandoned their traditional spring stopover sites owing to the disturbance caused by hunting activities, and they were far more wary than before. Along marsh edges I often found dead hawks that probably had happened to stray too close to a goose blind; somehow, many waterfowl hunters still have the medieval idea that the only good hawk is a dead one. I felt ashamed that for a few years as a youngster I, too, had eagerly hunted ducks with my brother and father, until I was able to buy my first long-lens camera.
Since the late 1990s I have come to accept the idea of spring hunting of snow geese as one of the inescapable aspects of modern life, brought on by an ever-expanding human population, an associated increase in human violence, and a decreasing understanding of the natural world. I have also realized that my 1975 book Song of the North Wind describes an environment that was rapidly changing and that the three decades since its publication have brought about massive increases in continental snow goose populations and distributions. These changes have directly resulted from various human environmental manipulations, including an increase in available food crops on the wintering grounds and spring migration routes, an effective system of wildlife refuges that produces locally massive concentrations of geese, and the gradual climatic warming of arctic breeding grounds that has greatly improved breeding success rates in these previously highly marginal nesting environments.
As a result, I decided that I must revise my snow goose book. In the summer of 2009 I reviewed the technical literature of lesser snow geese as well as the other “light geese” of North America, namely the smaller Ross’s goose of western Canada and the larger greater snow goose of eastern Canada’s high arctic. Neither was a part of my original story, but for various reasons the fates of these birds have become increasingly intertwined with that of the lesser snow goose and need to be considered with it.
The Southampton Island snow goose population (in northern Hudson Bay) that I described for my 1975 book consisted of about 156,000 breeding birds in 1973. By 1979 it had grown to 233,000, and by 1997 it had reached 716,000. Other major Canadian snow goose colonies include Baffin Island, with 1.76 million breeding birds by 1997, the central Canadian Arctic, with 816,000 in 1998, and the western Canadian Arctic, with 580,000 by 2002. Including immature birds and other nonbreeders, the lesser snow goose population in the eastern Canadian Arctic had reached nearly four million birds by the late 1990s. There were also about one million lesser snow geese in the central Canadian Arctic by 1998 and 753,000 in the western Canadian and Alaskan Arctic by 2002. In addition, up to about 100,000 snow geese nesting on northeastern Siberia’s Wrangel Island annually migrate through Alaska to winter in California’s Central Valley. There were thus probably at least five million lesser snow geese alive at the start of the twenty-first century.
The other light geese have also expanded their populations. The high-arctic and more easterly oriented greater snow goose population that mostly breeds farther north than the lesser snow goose and winters along the Atlantic coast first reached about one million birds by 2006. It had grown at an 8 percent annual rate since 1965 and attained an all-time high population estimate of 1.4 million by 2009. The Ross’s goose population of northwestern Canada also reached or exceeded a million birds by 2001. These population changes occurred remarkably rapidly. In 1965–67, thirty-seven snow or Ross’s goose colonies in the Queen Maud Gulf along the arctic coast of Canada’s Northwest Territories had 44,300 nesting birds, with 77 percent of them Ross’s geese. By 1988 there were fifty-seven colonies totaling 467,000 snow or Ross’s geese, with about 60 percent of them lesser snow geese. That twenty-three-year period saw a 7.7 percent annual rate of population increase among Ross’s geese and a 15.4 percent annual growth rate for lesser snow geese. Much of the snow goose’s remarkable increase probably resulted from immigration out of colonies in the eastern Arctic, since a 15 percent rate of annual increase in geese is much higher than would be possible through local reproduction alone.
In recent decades, refuge management changes, altered agricultural practices, and milder winters have had major effects on midcontinental snow goose migration patterns, as to both timing and major wintering sites. Far more snow geese now winter in the Missouri Valley of Kansas and adjacent Missouri than was the case in the 1960s. Many of these birds are from the Southampton Island colonies.
Snow geese occur in both white and blue phases. During the 1950s the incidence of blue-phase birds in the Southampton Island colonies was 30–35 percent. Over the forty-year period from 1967 to 2006, blue-phase birds made up 27.5 percent of all the snow geese counted in the Great Plains region during Christmas Bird Counts. There is thus no evidence that either of these genetically based plumage types has shown a selective advantage over the other in correlation with changing arctic climates. And, although Ross’s geese historically were entirely of the white-plumage phase, a few blue-phase adults have been found in recent years. This very rare plumage variant in Ross’s geese, with a frequency estimated at no more than one in ten thousand birds, probably resulted from gene exchange during occasional hybridization with blue-phase snow geese.
American hunters were killing about a third of a million snow geese in the Mississippi and Central Flyways during regular hunting seasons of the late 1960s. At that time the midcontinent population of snow geese totaled about 1.5 million birds. Since 1972, when both flyways had daily shooting limits of only four snow geese, the continental light goose populations have all shown almost continuous proportional increases, and hunting regulations have been relaxed accordingly. In the Central Flyway states between North Dakota and Texas, daily bag limits were increased from five to seven birds in the 1980s and to ten birds in 1992. The waterfowl hunting season was also increased from 88 to 107 days, the maximum permitted by the Migratory Bird Treaty between the United States and Canada. Changes in this treaty during 1995 permitted the extension of the snow goose hunting season to March 10 in part of the Central Flyway, although in Nebraska the first spring season didn’t take place until 1998. Other restrictions were also relaxed, including even-larger or unlimited daily bag limits, allowing shooting to continue until a half hour after sunset, the use of electronic calls to help entice geese into shotgun range, and permitting more than three shells in shotgun magazines.
By the mid- to late 1990s the midcontinent snow goose population had reached about three million birds. It was eventually decided by conservation agencies of both the United States and Canada that the lesser and Ross’s goose populations should be reduced to half the late 1990s levels, and the greater snow goose population to five hundred thousand birds. Annual kills of these so-called “light” geese in the United States and Canada gradually increased from an average of 581,000 during the 1980s to more than a million between 1998 and 2002, as hunting regulations were relaxed and seasons extended. Special goose seasons between 1998–99 and 2001–02 thus helped increase the total continental light goose kill to an average of 1.3 million over the first four years of these “Conservation Order” hunting seasons.
These progressively increased opportunities for late winter and spring goose hunting were balanced by an increasing wariness of the geese and other compensatory factors, since total light goose kills leveled off and have declined somewhat after reaching a high point of 1.55 million during the 1999–2000 season. For the four-year period between 2005–06 and 2008–09, the combined U.S. and Canadian snow and Ross’s goose kill averaged 890,000, or only about 60 percent of the record 1999 numbers. Considering the continued spectacular increases in light goose numbers in spite of this high level of hunter-caused mortality, the targeted population levels just mentioned for all three goose populations are unlikely to ever be reached through even more liberalized hunting regulations and expanded seasons. It also seems unlikely that these changes encouraging ever more lenient goose killing have engendered any new hunter understanding of and respect for their prey or for nature generally.
Snow geese populations in the Great Plains have not only increased tremendously in the past few decades, but many have also shifted their spring migration pattern from the Missouri River at least one hundred miles west into the central Platte Valley. This route change has brought more than a million snow geese into contact with several million sandhill cranes, cackling geese, Canada geese, and greater white-fronted geese. Snow geese and other geese usually arrive in the valley slightly earlier than do the cranes, and they are more prone to forage in the Rainwater Basin south of the Platte than to be concentrated like the cranes to the immediate Platte Valley. However, snow geese certainly compete directly with both cranes and other geese for corn throughout that region, as well as with an expanding deer population.
The geese and sandhill cranes have greatly benefited from the revolution in corn-growing technology in the Platte Valley, where production increases of about sixfold followed World War II. Greatly expanded irrigation, fertilization, and chemical pest management have all combined to produce a corn-growing bonanza in that region and have helped make Nebraska one of the major corn-growing states in the country. By the end of the twentieth century, record-setting annual corn crops were being grown statewide, with the Platte Valley responsible for nearly 40 percent of the state’s total crop output. Between 1998 and 2003 the average annual state corn production was 1.1 billion bushels, and between 2004 and 2009 it averaged 1.4 billion bushels, or more than 150 bushels per acre. Assuming a harvesting efficiency of 90 percent, there would be about fifteen bushels per acre left in the field for wildlife to consume.
This food bonanza attracted a crowd. Although in the early 1970s an estimated 200,000 sandhill cranes staged there during spring, by the early 1980s crane numbers had increased to about 250,000, of which perhaps 200,000 were arctic-bound lessers. By the late 1990s maximum spring crane counts in the Platte Valley approached or exceeded 500,000 birds, although subsequently the population has apparently stabilized.
Evidence has been accumulating that, during their time in Nebraska, these midcontinent sandhill cranes are now unable to accumulate the levels of fat reserves that they had achieved in the 1960s and 1970s. This is probably the result of increased food competition among the millions of geese and cranes and a progressively improving corn-harvesting technology. Like the snow geese using the Platte Valley, the sandhill cranes are probably also now departing for their tundra breeding grounds in less-than-optimum breeding condition. But, like lesser snow geese, they have also benefited from the recently warming weather conditions in the Arctic during nesting and have continued to achieve successful reproduction.
Larger populations and increased hunting of midcontinent cranes since the 1960s have resulted in a recent annual hunting mortality (including those shot but not retrieved) approaching a record number of forty thousand birds, which represents most of this population’s overall annual recruitment. The current near stability, if not decline, of the crane population makes it less likely that they will experience a population disaster such as that now facing snow geese. Because of the high level of use of the Platte Valley by endangered whooping cranes, sandhill crane hunting has never been allowed in Nebraska. For the same reason, spring goose hunting is also not allowed along a several-mile-long corridor on both sides of the river, which thus provides a safe feeding and roosting sanctuary for the cranes as well as other birds. The result is a spring bird spectacle perhaps now unmatched anywhere in the world, and one occurring only a few hundred yards off I-80! If I could have my wishes fulfilled, one would be that all Nebraskans might visit the central Platte Valley during March and, armed only with binoculars or a camera, absorb the sights and sounds of our state’s most unique, most beautiful, and most fragile natural treasure.