The Black Scoter (Melanitta americana) is a large sea duck found in North America. It breeds in the far north of Canada and Alaska and migrates south along the Pacific and Atlantic coasts to winter as far south as California and North Carolina. The Black Scoter is considered a rare bird in many parts of its range due to declining populations over the past few decades. In this article, we’ll look at the status and distribution of Black Scoters, what makes them rare, and some of the conservation issues facing this species.
What is a Black Scoter?
The Black Scoter is a stocky, black and white sea duck with a large black bill. The male has all black plumage with a yellow or orange bill knob during breeding season. Females are brownish-black with white around the base of the bill and on the nape. Black Scoters feed by diving underwater to catch mollusks, crustaceans, and aquatic insects. They nest on the ground near inland waterbodies and winter in large flocks in coastal marine habitats.
Black Scoter Distribution and Population Trends
Black Scoters have a circumpolar distribution, breeding in Alaska, across northern Canada, and in Iceland, Scandinavia, and Russia. In North America, key breeding areas include northern Alaska, the Yukon, Northwest Territories, Nunavut, Quebec, Labrador, and Manitoba.
The North American population of Black Scoters has sharply declined since the 1950s, with surveys estimating a population drop from around 400,000 birds in the 1950s to only about 200,000 by the early 2000s. Breeding Bird Survey data indicates an annual population decline of 2.2% per year from 1966 to 2015.
This decline has led to the Black Scoter being listed as a species of Special Concern under the Canadian Species at Risk Act in 2001. It has also been identified as a Bird of Conservation Concern by the U.S. Fish and Wildlife Service.
Why are Black Scoters Considered Rare?
Black Scoters are considered rare throughout much of their breeding and wintering range. There are several reasons behind their declining numbers:
– Habitat degradation and loss – Wetland drainage on breeding grounds and coastal development on wintering areas has reduced habitat availability.
– Overhunting – Black Scoters were heavily hunted for food and the feather trade in the late 1800s and early 1900s. Some wintering populations are still hunted today.
– Oil spills and marine pollution – Black Scoters are vulnerable to oil spills in coastal habitats and ingestion of marine plastics can impact health.
– Sensitivity to human disturbance – Black Scoters avoid nesting near human activities and are prone to flushing from feeding and resting areas near marine traffic.
– Low reproduction rates – Black Scoters have naturally low clutch sizes of around 5-7 eggs. Nest success is typically only 50% due to predation. Their limited reproductive potential makes it hard to rebound from population declines.
As a result of these threats, both the distribution and total numbers of Black Scoters have become limited. They are now rare and local in many parts of their historical range.
Status as a Rare Bird in North America
To understand the rarity status of Black Scoters in more detail, we’ll look at their seasonal distribution and key wintering and breeding areas across North America.
Winter Range and Status
On their coastal wintering grounds, Black Scoters range along the Pacific Coast from Alaska to Baja California. On the Atlantic Coast, they winter from Newfoundland and the Gulf of St. Lawrence south to North Carolina.
Some key wintering sites and concentration areas for Black Scoters include:
– Pacific Coast: Puget Sound, San Francisco Bay, Strait of Georgia
– Atlantic Coast: Bay of Fundy, Cape Cod Bay, Chesapeake Bay
Black Scoters occur in the highest winter densities in Alaska, British Columbia, and Washington State on the Pacific Coast. On the Atlantic, large winter flocks congregate in the Bay of Fundy between Maine and Nova Scotia.
Overall winter numbers in the contiguous U.S. are estimated at only around 30,000 birds. Breeding season surveys indicate that Pacific birds only comprise about 10-15% of the continental population while the rest are Atlantic birds. Due to these relatively small wintering numbers, the species is considered rare throughout most of its U.S. winter range.
Breeding Range and Status
During the breeding season, Black Scoters nest across Canada and Alaska. The densest breeding populations are found in the following regions:
– Western Alaska – Lower Yukon River Delta
– Central Canada – Northwest Territories, Nunavut, and Hudson Bay Lowlands
– Eastern Canada – Central Quebec, Labrador, Island of Newfoundland
Nesting Black Scoters are rare and very local in the northern U.S., with just a few hundred pairs nesting in northern Minnesota, Wisconsin, and Michigan.
Overall, it’s estimated that only about 10-20% of the global population breeds in the lower 48 United States. Their breeding range is limited to small portions of the northern U.S. border states. The vast majority of the species nests in remote regions of Canada and Alaska.
Endangered Species Status
While the Black Scoter is considered a rare species of conservation concern, it has no formal endangered species status or protections in the U.S. or Canada. However, it is categorized as an IUCN Red List Vulnerable species due to the large population declines over the last few decades. Some organizations have petitioned for the Black Scoter to be federally listed under the Endangered Species Act in the U.S., though it has not yet received this status.
Rarity Summary
In summary, the Black Scoter is considered rare throughout most of its range due to declining bird numbers resulting from a variety of threats. It has a limited winter distribution and breeds sparsely in the contiguous United States. The species has disappeared entirely as a breeding bird from portions of the southern edge of its range. Most of the population is found in Canada’s northern territories where ongoing monitoring and protection of key sites will be important for conservation of this rare sea duck.
Black Scoter Identification
Identifying Black Scoters amidst a raft of seaducks can be tricky. Here are some tips to help pick out these dark, stocky divers:
Field Marks
– Male is entirely black with yellow or orange bill knob in breeding plumage. Dark brown in eclipse plumage.
– Female is dark brownish-black with pale cheeks and nape. Dark cap contrasts with light face.
– Thick, bulging dark bill has a flattened top profile (vs. more pointed bill of other scoters).
– Stocky, short-necked profile on the water. Sits low in the water when resting.
– White secondaries flash on the wings in flight.
Similar Species
– Male Black Scoter similar to male White-winged Scoter but lacks white on the face.
– Females resemble female Surf Scoters but Black Scoter has dark cap, lighter nape and more rounded head shape.
– Significant white on the wings helps distinguish from female Common Scoter in flight.
Behavior
– Forms dense flocks on coastal waters during winter and migration.
– Makes direct, steady flights low over the water. Flocks appear in lines or V-shaped groups.
– An expert swimmer and diver, often forages deeply underwater.
– Tends to dive abruptly without much surface preamble.
– Migrates in shallow, rapid wingbeats in long chains of birds.
Habitat
– Pelagic – Found on bays, coastal waters, offshore during migration and winter.
– Lakes & Rivers – Nest and breed on inland freshwater lakes, ponds, and rivers.
– Shoreline – Rests along undisturbed rocky or sandy shorelines.
Feeding Behavior
– Feeds heavily on mollusks like clams, mussels, and snails during the non-breeding season. Will also take crustaceans and fish.
– Makes deep dives to the seafloor to forage on bottom-dwelling prey. Can dive to depths of 130 feet.
– Surface feeds less often than other scoter species, doing more diving for food.
– Nocturnal feeding tendencies; more active foraging occurs at night.
Vocalizations
– Generally silent. Male has a squealing courtship call.
– Low grunting or hoarse croaking noises made during courtship displays.
– High-pitched, squeaky growling indicates aggression between competing males.
Black Scoter Nesting and Reproduction
The breeding behaviors and nesting habits of the Black Scoter provide insights into their rarity and vulnerability:
Nest Sites
– Nests on the ground concealed in dense vegetation near water – usually on islands or peninsulas.
– Nest located in sites with grasses, willow thickets, or shrubby forest areas.
– Prefers to nest in concealed sites safe from land predators.
– Will use elevated nest platforms where available. Readily uses nest boxes.
Courtship and Pairing
– Courtship occurs on lakes and ponds in April/May during spring migration.
– Males perform displays – head-throwing, neck-stretching, tail-cocking. Give high-pitched whistles and grunts.
– Monogamous. Pair bonds form on breeding lakes before females disperse to nesting areas.
Egg Laying
– Peak egg laying in late May through early July depending on latitude.
– Clutch of 5-7 eggs (occasionally up to 10). Eggs creamy white in color.
– Eggs laid at interval of 24-48 hours. Female incubates for about 28 days.
Nesting Success
– Nest success averages around 50%, less than other ducks – likely due to high predation rates.
– Foxes, mink, gulls, jaegers, and bears are common nest predators.
– Females have strong nest fidelity and may re-nest up to two times if early nests fail.
Duckling Rearing
– Female alone cares for the brood and leads them to water after hatching.
– Ducklings fledge at 55-65 days, later than many other ducks.
– Duckling survival rates are poorly known but likely low.
– Annual adult female survival is 85-90%, indicating lower recruitment of young.
Threats and Conservation Concerns
Understanding the conservation threats facing Black Scoters can help explain their decline and rarity. Some of the main concerns include:
Breeding Habitat Degradation
– Drainage of boreal forest wetlands for forestry and agriculture removes key nesting habitat.
– Mining and energy development encroaches on remote northern breeding lakes.
– Increased nest predation near human disturbance and developments.
Marine Habitat Degradation
– Coastal development destroys crucial wintering habitat along migration routes and wintering grounds.
– Oil spills have disproportionate impacts on seaducks.
– Offshore energy projects may displace birds from foraging sites.
Overharvest
– Historical hunting pressure depressed populations early in the 1900s.
– Ongoing subsistence and sport harvest in some areas may limit recovery.
Plastic Ingestion
– Scoters ingest mollusk shells to aid digestion of prey. May mistake plastic debris for food.
– Plastics reduce body condition and survival. A 2011 study found 89% of Black Scoters had ingested plastic particles.
Disturbance and Displacement
– Boat traffic causes disturbance and alters behavior. Chronic disturbance limits energy intake.
– Some key wintering sites like Chesapeake Bay have high rates of human activity.
Climate Change
– Breeding habitat suitability may decline at southern edge of breeding range as climate warms.
– Increased storms and flooding could imperil low-lying nest sites.
– Prey distributions may shift, affecting winter food availability.
Conservation Actions Needed
Several management strategies could aid Black Scoter conservation:
Habitat Protection
– Preserve and restore wetland breeding habitat, particularly in eastern boreal forests.
– Safeguard crucial wintering areas through reserves, restrictions on development, and managed public access.
Harvest Management
– Establish restrictive bag limits or hunting moratoriums in areas of concern.
– Implement mandatory harvest surveys and improve population monitoring to assess sustainability.
Mitigate Disturbance
– Restrict industrial activities near key breeding and molting lakes.
– Limit recreational boating and aircraft near high density wintering and migratory stopover areas.
Monitor Contaminants
– Assess impacts of plastic pollution and mitigate through fishing debris cleanup and restrictions on plastic usage.
– Continue evaluating levels of oil contamination, especially in known wintering hotspots.
Support Partnerships
– Strengthen international cooperation between the U.S., Canada, and Mexico to align conservation strategies across the species’ range.
– Engage indigenous communities in population monitoring and sustainable harvest programs.
Fill Research Gaps
– Better information needed on population trends, reproduction rates, migration patterns, and foraging ecology to guide targeted conservation projects.
Conclusion
The Black Scoter is considered a rare bird throughout North America due to declining populations stemming from a variety of threats and conservation challenges. This species faces degradation of its breeding habitat, pressures on its coastal wintering grounds, contamination from plastics and oil, overharvest, disturbance, and climate change effects. Conservation actions like protecting key sites, managing human activity, cleaning up pollution, setting hunting limits, and filling research gaps could aid recovery efforts. But the Black Scoter will likely remain a local and uncommon bird in most regions because of its specialized marine habitat needs and low reproductive potential. Continued long-term monitoring and protection of global populations will be required to ensure the future of this vulnerable seaduck.