Dickinson Ch17: Waterfowl

Twelve species of waterfowl are common in the southern forests of the United States.
Wood ducks and hooded mergansers are residents that breed locally.
Major species that winter and migrate through southern forests include the Mallard, black duck, northern pintail, gadwall, American wigeon, green-winged teal, ring-necked duck, and Canada goose.
Waterfowl use of southern forests is mainly confined to bottomland hardwood forests and associated wetlands.
Waterfowl are highly prized game birds.

Historical populations of the most common species, mallard and wood duck, were certainly greater than today.
Pre-settlement accounts indicate millions of birds wintered in the South. Wood ducks were the most abundant duck east of the Mississippi River during pre-settlement times.
The Mississippi Alluvial Valley (MAV) originally covered over 25 million acres of bottomland hardwood forests (BHF).
Less than five million acres of MAV forests remain, and they are highly fragmented.
The most rapid loss of BHF in the MAV occurred between 1950 and 1970, primarily due to clearing for agricultural production (crops, soybeans, aquaculture).
The construction of large reservoirs (1940-1970) destroyed thousands of acres of BHF and altered downstream hydrology, negatively impacting waterfowl habitats.
The status of waterfowl populations in North America is monitored annually through surveys, banding, and research.
Breeding duck numbers fluctuate seasonally, with the highest counts occurring in the 1950s, 1970s, and 1990s.
Currently, goose populations are generally high (with the exception of the Southern James Bay Canada goose population).
Mallard, gadwall, and northern shoveler populations are near or above historical averages, but populations of pintail, scaup, and blue-winged teal show long-term declines.

Waterfowl use a variety of habitats and rely on resources tied to seasonal cycles and specific events.
Wood ducks and mallards are highly mobile and readily move within and among regions in the South.
Waterfowl primarily use low elevation bottomland forest sites that flood only for extended periods during the dormant season.
Seasonal shifts in food resources are tied to the annual reproductive cycle:
- Early Fall: Moist-soil seeds (e.g., smartweed, millet).
- Late Winter/Spring: Invertebrates (e.g., crayfish, amphipods, isopods, mollusks), which provide crucial protein for breeding females.
- Midwinter: Acorns, grass, and aquatic insects.
Trophic Niche Examples:
- Carnivores: Hooded mergansers dive for fish, amphibians, and large invertebrates. Northern shovelers are filter feeders focusing on small aquatic invertebrates and plankton.
- Omnivores: Mallards and Wood ducks feed on acorns, seeds, and insects.
- Herbivores: Canada geese primarily graze. Gadwall and wigeon mainly eat aquatic vegetation.

Diseases that cause high mortality include avian botulism, avian cholera, lead poisoning, and duck virus enteritis (DVE).
- Avian botulism outbreaks occur during warm, late summer and fall when water levels fluctuate, often in large terminal river basins.
- Avian cholera, caused by Pasteurella multocida, is common in winter and spring.
Waterfowl are exposed to various contaminants, including lead and other heavy metals, pesticide residues, and PCBs. The restriction on the use of lead shot in hunting began in the late 1970s and 1980s.
Predation is generally low during the nonbreeding season but high during nesting and brood rearing.
Nesting predation of wood ducks and hooded mergansers (tree cavity nesters) by species like raccoons and mink is significant.

Waterfowl conservation focuses on six major areas: habitat protection/restoration, regulating sport harvest, disease management, pollution regulation, predator management, and propagating rare species.
The North American Waterfowl Management Plan (NAWMP) established population goals and objectives.
Harvest management relies on annual regulations based on population and status data.
A special type of managed habitat is the Green-tree Reservoir (GTR), which consists of forested bottomland habitat intentionally flooded in late fall or winter to provide food and habitat.
Hunting is a large tradition in the southern U.S..
In the 1995-96 season, approximately 460,000 adult hunters pursued waterfowl in 14 southern states.
The most harvested species of ducks were Mallards, followed by wood ducks. Wood ducks were the most harvested species in Georgia, South Carolina, and North Carolina.