By Mark Petrie, Michael Casazza, Chris Nicolai, and Cliff Feldheim
It’s been more than two decades since liberalized hunting regulations were introduced with a goal of reducing the number of light geese in North America, including lesser snow geese, greater snow geese, and Ross’s geese. In the United States, these new regulations were sanctioned under the Light Goose Conservation Order and were aimed at the rapidly increasing light goose populations thought to be severely altering habitats in some parts of the Arctic. The population reduction efforts were designed to prevent additional negative impacts on these habitats and potential adverse consequences for many other wildlife species that also depend on these ecosystems.
How successful was the conservation order in reducing light goose numbers? Were our fears about damage to the Arctic realized? Are goose populations done growing, or should we expect more birds in the future? Could goose numbers reach a point at which they compete with ducks for food on key wintering grounds? Let’s start with a short history of how we arrived at the conservation order in the first place.
In 1997, DU’s chief biologist at the time, Dr. Bruce Batt, coordinated with a group of waterfowl managers and scientists to produce a report entitled Arctic Ecosystems in Peril. The report chronicled the growth of light goose populations, described the changes they were causing to staging and nesting habitats, and ultimately provided justification for the conservation order. Most of the report focused on midcontinent lesser snow geese. These are birds that nest in the central and eastern Canadian Arctic and subarctic and winter in the Mississippi and Central Flyways. Based on counts made during winter, their numbers had increased from fewer than 1 million birds in the 1960s to an estimated 3 million birds by the mid-1990s. This population staged in salt-marsh habitats along the coasts of Hudson and James Bays, where they grubbed for roots and rhizomes during spring migration. By the late 1990s, the birds had denuded 130,000 acres of salt marsh and severely altered another 100,000 acres.
While light geese in the midcontinent population got most of the press, the report also highlighted the growth of greater snow goose populations from 25,000 birds in the 1960s to nearly a million birds by the late 1990s. Although greater snow geese breed in the eastern Canadian Arctic and mostly winter in the Atlantic Flyway, there was a growing fear that this population would also damage vegetation on staging and nesting habitats if left unchecked.
Finally, the report provided a clear explanation of why light goose numbers had increased so dramatically. In short, the birds had benefited from the expansion of agriculture on their migration and wintering areas, which provided them with an almost unlimited food supply. This allowed more birds to reach breeding age and more adults to return to the breeding grounds in better condition, which increased their productivity.
The conservation order went into effect in 1999. The goal was to reduce light goose populations by half over a 10-year period by greatly increasing daily bag limits and allowing hunting after March 10. It also permitted the use of electronic calls, unplugged shotguns, and hunting until a half hour after sunset. Spring conservation seasons for light geese were also implemented in Canada.
Success of Liberalized Hunting Regulations
The special harvest regulations enacted for light geese were aimed at reducing survival of adult birds. The potential for a population to persist is strongly influenced by adult survival rates—when more adults in the population survive, there is greater potential for the population to remain steady or even grow if new geese are produced at a faster rate than the rate at which adult birds die. Harvesting juvenile geese does little to reduce the population, because few of them survive to adulthood naturally, and adults are responsible for gosling production.
Prior to the conservation order, hunters harvested about 2.5 percent of all adult lesser snow geese in the midcontinent population each year, or one in 40 adults. After the order was passed, harvest rates increased to about 2.7 percent, or one in 37 adults. Not surprisingly, this minor change in harvest rates had little impact on adult survival. Annual survival rates for adult geese actually increased following the conservation order, from 87 percent to 90 percent. Dr. Ray Alisauskas, a scientist with the Wildlife Research Division of Environment and Climate Change Canada, who estimated these survival rates, put it rather well when he said, “It seems that midcontinent lesser snow geese are very good at eluding death.”
So why did the conservation order fail to reduce adult survival for geese in this population? The simplest explanation is that the rapidly growing number of geese overwhelmed the ability of waterfowlers to increase harvest rates. When the conservation order was passed, the number of light geese in the midcontinent population was thought to be around 3 million total birds, based on winter surveys. But trying to count millions of birds in large, swirling flocks is very challenging. A more rigorous estimation method that relies on harvest information and band recoveries reported by hunters suggested that visual counts during winter greatly underestimated the number of birds, and that there were in excess of 8 million (possibly as many as 20 million) adult lesser snow geese in the midcontinent population. That is a completely different ball game, and even the most liberalized hunting regulations stood little chance of keeping such a large population in check.
Although the conservation order substantially increased the overall light goose harvest, that harvest has been declining in recent years, and the probability that an average adult goose will be shot has remained virtually unchanged. It’s a classic story of “safety in numbers.” A typical snow goose flock is now populated with long-lived adults that have been exposed to multiple hunting seasons and the wisdom those seasons impart. That’s hardly a recipe for increasing adult harvest rates and lowering adult survival.
The story is different for greater snow geese, whose numbers had reached a million birds by the late 1990s. Prior to the conservation order, hunters harvested about 40,000 adult greater snow geese each year. That number increased to 100,000 birds immediately after the conservation order was passed, and this harvest level was generally maintained in the decade that followed. As a result, annual adult survival rates were reduced from 83 percent to 72 percent, which proved enough to stabilize the population. The success of this conservation order, versus that for other light geese, was largely due to it being enacted before the population became too large for hunters to control. Unfortunately, interest in pursuing greater snow geese appears to have waned in recent years. The number of spring hunters in Canada has declined by more than half, and harvest of greater snow geese on their Atlantic Flyway wintering grounds has also decreased.
Evaluating how successful the conservation order has been in reducing adult survival rates is obviously important. However, it’s equally important to consider how the population size of light geese has actually changed since the order went into effect. Alisauskas recently estimated the number of adult lesser snow geese in the midcontinent population from 1970 through 2018. He focused on adult birds because, as we saw earlier, the potential for this population to grow strongly depends on the number of adult geese. Adult numbers increased through about 2010 and have generally declined since then. Most of this decline is attributed to a recent string of Arctic weather unfavorable to the survival of young geese. These weather conditions don’t increase mortality among adult birds, but they do prevent adult birds that might die during the rest of the year from being replaced by juvenile birds.
Damage to Arctic Habitats
Concern about the damage geese were doing to Arctic habitats prompted the original conservation order. Dr. Jim Leafloor, a Canadian Wildlife Service biologist with Environment and Climate Change Canada, has nearly three decades of experience in the Arctic, and his perspective has changed over the past 20 years. “Initially, there were concerns about damage to Arctic habitats by geese, and there is no doubt that this has occurred in some places,” Leafloor says. “However, the most heavily impacted habitats were the coastal salt marshes of James Bay and Hudson Bay. Although these areas are important to geese, they represent only a tiny fraction of what is used by geese during summer. Moreover, much of the damage was due to high concentrations of snow geese and Canada geese that use these coastal habitats during spring migration. Freshwater habitats support the vast majority of Arctic-nesting geese during most of the summer, and most of these habitats do not show widespread damage from goose foraging. It remains a possibility that coastal salt marshes are crucial habitat for migrating geese and other species, like shorebirds, but at the same time we continue to see years of widespread production by snow geese in years when nesting conditions are good.”
Leafloor’s observations lead to an important question: Should we expect more geese in the future? Although some light goose populations have been reduced because of poor weather in the Arctic, that situation will almost certainly change. Good weather will replace bad, more goslings will be fledged, and these same populations will likely resume their march forward. This is supported by Leafloor’s belief that most of the traditional nesting colonies have not suffered serious damage from overgrazing, and thus retain their potential to raise geese.
Leafloor also believes there is room in the Arctic for more geese outside these traditional nesting colonies. “I do believe that there is considerable room in the Arctic for more geese, but there is also evidence that some of the traditional nesting areas may have reached capacity,” he says. “Future growth of some light goose populations may require dispersal into unoccupied habitats, such as areas of Alaska, where gosling survival is high and there is no evidence of habitat limitation. Most of the best goose habitat has probably been occupied in the Arctic, but there is still a lot left where densities are very low.” His thoughts are echoed by other goose researchers who believe that getting a better understanding of how many geese the Arctic can ultimately support should be a top priority.
Competition on Wintering Grounds
If we assume that the Arctic can produce more geese, and that hunting will struggle to curb population growth, we are faced with new questions much closer to home. Fifty percent of all dabbling ducks in the United States winter in just three areas—the Central Valley of California, the Gulf Coast, and the Lower Mississippi Alluvial Valley. Agricultural foods, especially rice, are an important source of food energy for ducks in each of these regions. Geese like rice too, along with pretty much every other farmed grain. The supply of agricultural foods in these major wintering areas is not infinite, so at what point do ducks and geese begin competing for these winter food resources?
The Central Valley is a case in point. Winter-flooded rice, or rice fields that are flooded after harvest, provide half of all the food available to ducks in this region. The number of geese wintering in the valley has more than doubled in the last decade, from 1.1 million to 2.3 million birds. Most of these birds are lesser snow geese from Wrangel Island, the western Canadian Arctic, and Alaska, along with Ross’s geese and white-fronted geese. There are now enough geese in the Central Valley to eat every grain of rice that remains after harvest. Geese don’t currently have the opportunity to do so, because ducks are feeding alongside them, but the point is important.
Luke Matthews, a graduate student at the University of California–Davis, estimated that the average rice field in California contains 290 pounds of waste rice per acre shortly after harvest. However, ducks don’t usually feed in dry rice fields; they wait until the fields are flooded, which doesn’t occur until a month or more after harvest. By that time, Matthews estimated, the fields are down to 132 pounds per acre. Where did the rest of the rice go? Geese do feed in dry rice fields, and it’s likely that much of this loss is due to geese. In fact, biologists are starting to view geese as a form of habitat loss for ducks in the Central Valley.
Ethan Massey, a former graduate student at the University of Arkansas at Monticello and now a DU biologist, reached a similar conclusion for ducks and geese in Arkansas. “Early-migrating whitefronts consume substantial amounts of rice grain in both flooded and dry rice fields in October,” Massey says. “Dry fields are considered unavailable to ducks, but they may be flooded for duck habitat later in the wintering period. However, early-arriving Arctic geese may have already depleted these fields prior to flooding.” In some cases, geese can completely remove any of the cover or rice stubble in a field, making it far less attractive to ducks.
In 2018, Ducks Unlimited partnered with ConocoPhillips, California Department of Water Resources, US Geological Survey, California Waterfowl Association, US Fish and Wildlife Service, and California Department of Fish and Wildlife to begin a study aimed at answering two fundamental questions: How do geese impact duck food resources in the Central Valley, and should we expect more geese in the Central Valley in the future? As part of this study, lesser snow geese, Ross’s geese, and white-fronted geese were captured and fitted with GPS transmitters. These transmitters allow researchers to track a bird’s movements from the Central Valley to Arctic nesting grounds and back, providing two years of continuous data.
Marking geese with transmitters serves several purposes. First, it helps refine our understanding of the nesting colonies that supply the Central Valley with geese. Eventually we’ll evaluate these colonies to determine if they are near capacity or if they can support more geese in the future. Second, this technology allows us to track the daily movements of geese within the Central Valley to evaluate their habitat use and obtain a clearer picture of how they are competing with ducks for food.
We’ll also improve our understanding of goose diets and monitor the depletion of important waterfowl foods, including rice, to determine if ducks may face food shortages if goose numbers continue to rise. Diet information obtained from an earlier study of white-fronted geese in the Central Valley revealed that rice was their main food source from October through January before they switched to mostly green browse. The diminished importance of rice after January suggests that most of this food was gone. The ability of geese to switch to green browse is significant because it probably represents an almost unlimited food supply for them in late winter and early spring, though ducks don’t eat it. This becomes important when we consider how many additional geese the Central Valley might one day hold.
While our efforts to reduce light goose populations have resulted in mixed success, passage of the conservation order was unquestionably crucial in raising awareness about expanding light goose populations and their habitats. That awareness is leading to new questions, many now centered on the potential consequences to ducks. Finding answers will require new scientific investments as we continue to tackle the light goose dilemma.
Dr. Mark Petrie is director of conservation planning in DU’s Western Region. Michael Casazza is a research wildlife biologist with the US Geological Survey’s Western Ecological Research Center. Dr. Chris Nicolai is a waterfowl scientist with Delta Waterfowl. Cliff Feldheim is chief of the Suisun Marsh branch of the California Department of Water Resources. The authors wish to sincerely thank Dr. Ray Alisauskas and Dr. Jim Leafloor. This article would not have been possible without their knowledge of light geese and the Arctic habitats on which these birds rely.