One motivation for understanding the population dynamics of any species, including birds such as grouse or wildfowl, is the concept of “doomed surplus”—the birds that die naturally each year, mainly young individuals (Errington 1946). This is based on the recognition that most young individuals fail to survive to breeding age and that populations are maintained near their carrying capacity through density-dependent processes (chapter 10). In theory, killing or capturing the doomed surplus makes no difference to the size of the adult population, and this idea has been incorporated into conservation in two main ways.
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The second way that harvesting birds has been incorporated into conservation is through recreational hunting. While this might seem paradoxical, hunting can be sustainable. On many private estates in Britain, for example, the harvest of nonmigratory game birds such as red grouse [Willow Ptarmigan], Black Grouse, and Western Capercaillie is effectively managed (albeit through the destruction of predatory birds). In North America the management of migratory ducks has also been successful. In 1934 the Migratory Bird Hunting Stamp Act was passed in the United States, meaning that federal licenses were required for hunting migratory waterfowl. All waterfowl hunters over sixteen must annually purchase and carry a Federal Migratory Bird Hunting and Conservation Stamp (or “duck stamp”). As well as allowing hunters to continue their pursuits legally, the scheme has had significant conservation benefits: 98 cents from every dollar goes toward the purchase or lease of wetland habitat in the National Wildlife Refuge Program, and since 1934 more than $750,000,000 has gone into the fund, enabling the purchase of more than 5.3 million acres of breeding, migration, and wintering habitat.
Ducks Unlimited was also created by hunters. Founded in 1937 during an intense drought that caused many waterfowl populations to nose-dive, its aim is to preserve habitat and ensure an abundant supply of waterfowl for the future. Ducks Unlimited is the world’s largest private waterfowl and wetlands conservation organization and has conserved more than 12.5 million acres of habitat across North America.
