Black Scoter: A tough and spunky little sea duck

I love this time of year. This period before freeze-up offers a chance for close looks at many of our diving sea ducks that linger in nearshore waters to feed enroute to their wintering areas.

In spring, most sea ducks rush by in elegant breeding plumage, in a hurry to reach their nesting grounds. But now some can be seen up close, diving energetically, chasing prey and each other, and riding big waves into crashing surf after fall storms.

Along rocky shorelines and jetties, in unfrozen river mouths, and sometimes in Nome’s harbor, one can often find mixed flocks of king, common, spectacled and occasionally Steller’s eiders, long-tailed ducks, white-winged scoters, and the focus of this article––the spunky, little black scoter.

Black scoters are one of North America’s least studied sea ducks. They nest in remote ponds and small lakes scattered across tundra and taiga regions of western Alaska and eastern Canada.

In this region, they breed near upland ponds and lakes, widely scattered across the Seward Peninsula. In 1989, when Kessel wrote Birds of the Seward Peninsula, Alaska, black scoters were described as fairly common breeders on the peninsula. I don’t know if that remains true today. In my limited orbit, they seem not as common as they once were.

The main movement of black scoters into Seward Peninsula waters is usually in the last week of May. Flocks stream by, low along the coast. The males are distinctive in their velveteen, all-black plumage with bright-orange, knobbed bills. Flocks can often be seen then in Safety Sound, where they rest and refuel before dispersing to their nesting ponds.

Black scoters arrive already in pairs. They are monogamous for the season, and it isn’t known whether pairs reform from year to year.

On the nesting ground, females choose the nest site, back from a pond’s edge, usually hidden in a clump of grass or beneath branches of a low shrub. Their nests are notoriously hard to find.

The female makes a depression in the ground, which she lines with grass and down. Peak egg laying is during the last ten days of June, which is later than for many ducks. The hen lays an average of seven eggs at about 36-hour intervals and begins incubation when the last egg is laid. During this time, the male guards her closely, chasing away any intruding males. And if females approach their nest site, the hen drives them away.

When the clutch is complete and incubation begins, males leave the breeding ground and the female alone incubates the eggs and cares for the young.

On the Seward Peninsula, peak hatch is during the last week of July after about 28 days of incubation. The downy, open-eyed ducklings leave the nest as soon as they are dry. The female leads them to the pond where they are able to catch insect larvae and feed themselves.

The hen tends her brood attentively for one to three weeks, brooding the chicks at night when they are small. Then, most females abandon their young before they can fly and return to the coast to molt.

The young stay on their natal pond, often congregating with other broods on the pond until they fledge at about six weeks of age. On the Seward Peninsula black scoters typically fledge around the second week of September.

Studies have found that the black scoter’s diet is about 90 percent animal matter and 10 percent plant materials.

During the breeding season on freshwater ponds, they feed on aquatic insects and their larvae, small mollusks and crustaceans such as amphipods, small fish, fish eggs and aquatic vegetation.

At sea during the rest of the year, black scoters eat mostly mollusks, such as mussels and clams, and also crustaceans, small fish, and herring roe when available.

They feed in open nearshore waters usually at depths of less than 30 feet. Black scoters forage by diving and swimming underwater, propelled by their big feet with wings folded or partly opened. They swallow their prey whole, usually while underwater. Powerful muscles in their gizzard crush their food—shells and all.

When male black scoters leave their breeding ponds, they first gather in flocks with other male scoters, long-tailed ducks and greater scaup in places such as the lower Serpentine River and Imuruk Basin. They soon move to estuaries and nearshore coastal waters before departing for molting grounds, perhaps joining huge flocks of molting scoters off the Yukon-Kuskokwim Delta.

Few black scoters are seen in the peninsula’s coastal waters between mid-July, when the males leave, and September, when juveniles fledge from their inland breeding ponds. Most depart quickly on fall migration but some linger along the coastline, as they are now.

It is not known where black scoters from the Seward Peninsula winter, but the species commonly winters along the north side of the Alaska Peninsula, along the Aleutian Chain, and in south coastal Alaska.

There is no recent population estimate for black scoters in Alaska. They nest in remote areas, and aerial surveys on the wintering grounds combine all three scoter species. These factors make population estimates and trends hard to determine.

Between the 1950s and the early 2000s, surveys in western Alaska indicated black scoters had declined by 50 percent. Surveys conducted from 2004 to 2015 suggested the population had stabilized, but more recently numbers are thought to be declining.

Many northern seabirds are in decline as warming oceans disrupt marine ecosystems and food chains the birds depend upon.

The International Union for the Conservation of Nature lists the black scoter as “Near Threatened." In 2017 Audubon Alaska placed the black scoter on their Red List of declining species of greatest concern.

The song of a black scoter recorded at Salmon Lake can be found here: https://macaulaylibrary.org/audio/141084