Frank C. Rohwer
Waterfowl managers face an unusual situation with the midcontinent population of snow geese – there are just too many. Some estimates have the population of these geese that winter in the central part of the United States, especially in Louisiana and Texas, at more than three million. Only a few decades ago, wildlife professionals were still doing all they could to help these beleaguered geese rebound from overhunting in the early 1900s. For example, they closed seasons or restricted harvests. To improve habitat the U.S. Fish and Wildlife Service allocated money from the federal duck stamp program to purchase several refuges in wintering areas and on the migration route.
Then, something rather inadvertent happened about 30 years ago. The snow geese finally discovered the smorgasbord of modern agriculture and adjusted their behavior so that life in the winter became a lot easier. Traditionally, the geese wintered in coastal marsh areas where they used those short but very strong bills to dig the roots of marsh grasses for dinner. The first transition was to rice fields, where the geese could graze on weeds and eat the grain left behind by the combine. A decade later the geese had mastered field feeding and had diversified into wheat, corn, sorghum and practically any other field grain they encountered. The geese had also begun to graze in fall-seeded grain fields, especially winter wheat. Snow geese now feed in grain fields as soon as they reach the prairies in September, and they continue to use agricultural fields until they leave the prairies in April and May on their way to arctic breeding areas.
Many biologists think the shift in winter feeding has led to the overabundance of geese. Winter may be the time of year that sets the upper limit to goose populations. Now, the abundance of waste agricultural grain has provided snow geese with excellent forage and has improved the survival of wintering geese. The national wildlife refuges bought to protect habitat also help to increase survival. Therefore, more geese are returning to the Arctic to breed each spring. Those returning geese are in much better physical condition than was the case when geese did not use agricultural grain but foraged in marshland. Geese are large enough that they can pack a lot of food with them when they leave the prairies. It is carried as large amounts of stored fat. This stored fat allows geese to lay more eggs and have higher nesting success than was possible when geese used natural habitats. Higher survival and birth rates mean a population is going to grow rapidly.
At first, this was a great success story for wildlife management. But too much of a good thing can turn out to be not so good. About 15 years ago biologists working with snow geese and other birds breeding in the Arctic tundra began to see some serious habitat degradation. When the snow geese get back to the Arctic they revert to feeding in their traditional style of grubbing out roots and rhizomes of sedges and grasses. There are now so many geese at some of the breeding colonies that vast acreages of formerly productive river delta habitats have been converted to mudflats. Because arctic growing seasons are short and the tundra so fragile, recovery of these mudflats may take several decades. The snow geese are able to keep moving, so local fauna bear the brunt of this habitat destruction.
In the early 1990s, the habitat problems in the tundra started to get out of hand. The vast flocks of snow geese coming south were also causing some depredation problems for winter wheat farmers in the Mississippi Flyway. Studies of goose population dynamics strongly suggested that the best way to slow or reverse the growth of the snow goose population was to increase the mortality rate of adults. That sounds easy, but those who hunt snow geese know this is not so simple. Unlike Canada geese and white-fronted geese (also known as “specks”), snow geese are unpredictable and tend to stay in very large flocks. Both traits make hunting difficult.
This is the point where researchers with the U.S. Geological Survey and the LSU AgCenter became involved. They examined use of electronic calls, which had been illegal for all waterfowl hunting. This research showed that electronic calls would greatly aid snow goose hunters. The research design involved coordination with hundreds of hunters to organize experimental hunts where every 15 minutes they switched between using an electronic call and not using this call. When the electronic call was turned on, the harvest rates – geese shot per hour by a hunter – were 9.1 times the harvest without the electronic call. Based on this research, managers and policy-makers pushed for legalization of electronic calls for snow goose hunting. This occurred in 1999.
Another study by USGS and AgCenter researchers examined a potential concern with the use of electronic calls. Some managers, especially in southern Canada, feared that electronic calls for snow geese might attract Canada and white-fronted geese, which could elevate their harvest rates to unacceptably high levels. To test this idea the scientists did experimental hunts in Manitoba and Saskatchewan, Canada. Again, the results were dramatic. When the electronic snow goose call was being played, it proved to be a fairly strong deterrent to Canada and white-fronted geese. This research was instrumental in the decision by the Prairie Provinces of Canada to legalize electronic calls in an effort to increase snow goose harvest.
The big question is whether the increased hunting effort, which extends into the spring, is having the desired impact. The preliminary results are promising. Sport hunters have greatly increased their harvest of snow geese. More important, the population has declined somewhat since 1998. Meanwhile, scientists are continuing to undertake research on snow geese and other waterfowl to supply the information needed to manage waterfowl populations.