The black scoter and the ruddy duck are two species of diving ducks found in North America. While they occupy some of the same habitats and have some similar behaviors, there are distinct differences between these two types of waterfowl.
Quick Answer
The black scoter is larger, mostly black and white in color, breeds farther north, dives deeper, and forms larger flocks than the ruddy duck. The ruddy duck is smaller, more brown in color, breeds farther south, is a stiffer tail when swimming, and the male has a bright blue bill during breeding season.
Size and Physical Description
The most noticeable difference between the black scoter and the ruddy duck is their size and color patterns.
The black scoter is the larger of the two species. It measures 18-21 inches long with a wingspan of 32 inches and weighs 2-3 pounds on average. The plumage of the black scoter is mostly black with a white spot near the base of the bill. The black feathers have a glossy iridescence on the back and wings. The female is a slightly duller brown than the male. The black scoter has a long black bill and yellow eyes.
In comparison, the ruddy duck is much smaller at 15 inches long with a wingspan of 22 inches and weighs just over 1 pound. True to its name, the ruddy duck has mostly reddish-brown plumage with a light blue bill for most of the year. During breeding season, the male has a striking sky blue bill, black cap, and bright white cheek patch. The female is all brown.
Physical Trait | Black Scoter | Ruddy Duck |
---|---|---|
Length | 18-21 inches | 15 inches |
Wingspan | 32 inches | 22 inches |
Weight | 2-3 pounds | 1 pound |
Color | Black with white spot | Reddish brown |
Bill Color | Black | Blue |
As you can see, the black scoter is noticeably larger than the ruddy duck in every physical dimension. Its size combined with its dark coloration makes it easy to distinguish from the smaller, brownish ruddy duck, especially during the breeding season when the male ruddy duck has its ornamental blue bill.
Range and Habitat
Another key difference between black scoters and ruddy ducks is their breeding and habitat ranges across North America. There is only partial overlap in where these species nest and winter.
Black scoters spend winters along both the Atlantic and Pacific coasts, with concentrations on the bays and estuaries of the Northeast U.S. and Alaska. They breed predominantly in Canada and Alaska and migrate north to nesting grounds on the taiga and tundra during summer. Their nesting habitat is generally near lakes, ponds, rivers, and marshes of the boreal forest and arctic tundra.
Ruddy ducks occupy a more southerly range for breeding. They nest throughout the prairie pothole region of the Northern U.S. and Canada during summer. Their wintering habitat extends from the Pacific Northwest through the Southern U.S. and into Mexico, mostly on inland freshwater lakes and marshes. There is overlap between the species on coastal wintering grounds and interior breeding grounds.
Range | Black Scoter | Ruddy Duck |
---|---|---|
Breeding | Northern Canada, Alaska | Northern U.S. and Canada |
Wintering | Coasts of Northeast U.S. and Alaska | Pacific Northwest to Mexico |
Habitat | Boreal forest, arctic tundra | Prairie potholes, inland wetlands |
The black scoter is more a northerly species, breeding in the arctic regions, while the ruddy duck sticks to more temperate areas for nesting. Their winter ranges overlap along the coasts but also diverge in some regions like the Southwest and Gulf Coast.
Diet and Feeding Behavior
As diving ducks, both the black scoter and ruddy duck feed primarily on aquatic invertebrates and vegetation. However, their diving behaviors and food preferences have some differences.
Black scoters are deeper divers than ruddy ducks. They routinely dive to depths of 60 feet or more searching the bottom sediments for mollusks, crustaceans, and other invertebrates. Their diet consists mainly of mussels, clams, snails, and insects. They will also eat aquatic plants and some small fish.
In contrast, ruddy ducks do not dive as deep, feeding closer to the surface in water 3-10 feet deep. They eat more plant material such as seeds of pondweeds and wild rice as well as aquatic insects and mollusks. Ruddy ducks will upend with their tails sticking up to feed on vegetation below the surface.
When feeding, black scoters tend to gather in large, single-species flocks numbering in the hundreds or even thousands of birds. Ruddy ducks form much smaller flocks, often associating with other diving ducks like canvasbacks.
Feeding Behavior | Black Scoter | Ruddy Duck |
---|---|---|
Diving Depth | Up to 60+ feet | 3-10 feet |
Diet | Mollusks, insects, crustaceans | Plants, insects, mollusks |
Flocking Size | Hundreds or thousands | Small mixed flocks |
The black scoter consumes more animal matter and dives much deeper in bigger single-species flocks. The ruddy duck is an omnivore feeding closer to the surface and forms smaller mixed foraging groups.
Breeding and Nesting
The breeding ecology and nesting behaviors of black scoters and ruddy ducks also show some variances based on their different habitats.
Black scoters nest in loose colonies on the ground by inland lakes and ponds of the northern boreal forest and tundra. The female builds a nest bowl out of available vegetation, down, and feathers lined with down. Black scoter clutches contain 6-10 eggs that are incubated for 24-28 days. Ducklings hatch synchronously and leave the nest within a day of hatching.
Ruddy ducks nest as solitary pairs scattered over the prairie pothole region. The female builds the nest in thick emergent vegetation near water, weaving a dome of cattails and reeds over the nest bowl. Clutch size is 5-15 eggs incubated for 23-27 days. Like black scoters, ruddy ducklings depart the nest quickly after hatching.
So while both are ground nesters, black scoters nest more colonially at higher latitudes compared to the solitary dispersed nests of ruddy ducks further south. But clutch size and incubation of the two species are fairly similar.
Nesting | Black Scoter | Ruddy Duck |
---|---|---|
Nest Site | Ground near water | Emergent vegetation |
Nest Type | Bowl in open | Domed in reeds |
Clutch Size | 6-10 eggs | 5-15 eggs |
Incubation | 24-28 days | 23-27 days |
The nesting strategies of black scoters and ruddy ducks differ in nest placement and structure but are similar in clutch size and incubation period.
Conservation Status
When it comes to conservation status, the black scoter and ruddy duck have some markedly different population trends and protection levels.
Black scoter populations have been in significant decline in recent decades. Habitat loss in breeding areas and exposure to oil spills and marine pollution on wintering grounds have caused numbers to drop. Black scoters are listed as a Species of Concern under the Endangered Species Act and considered a Priority Species by wildlife agencies. Conservation plans aim to reverse the downward trends.
Meanwhile, ruddy duck populations stabilized after declines last century due to overhunting and wetland loss. Their numbers rebounded with conservation actions like habitat protection and hunting regulation. Ruddy ducks remain widespread and common across their range.
Conservation Status | Black Scoter | Ruddy Duck |
---|---|---|
Population Trend | Declining | Stable |
ESA Status | Species of Concern | None |
Conservation Priority | High | Low |
While the ruddy duck is in good shape, the black scoter warrants ongoing conservation attention and habitat protection due to ongoing population declines.
Conclusion
In summary, the black scoter and ruddy duck exhibit clear differences in their size, coloration, geographic ranges, diving behavior, flocking patterns, diets, nesting habits, and conservation status:
- Black scoters are larger, mostly black and white ducks that breed in northern latitudes and winter along the coasts.
- Ruddy ducks are smaller, brown ducks that stick to more southern breeding grounds and inland wetlands.
- Black scoters dive deeper in bigger flocks and eat more mollusks and insects.
- Ruddy ducks feed closer to the surface in mixed flocks and consume more plant matter.
- Black scoters nest colonially on the open tundra while ruddy ducks nest singly in vegetated wetlands.
- Black scoter populations are declining while ruddy ducks are more stable and abundant.
Understanding these differences helps birders quickly distinguish these two diving duck species that may share some of the same watery habitats across North America.
References
[1] The Cornell Lab of Ornithology. “Black Scoter.” All About Birds. https://www.allaboutbirds.org/guide/Black_Scoter.
[2] Audubon. “Black Scoter.” https://www.audubon.org/field-guide/bird/black-scoter.
[3] The Cornell Lab of Ornithology. “Ruddy Duck.” All About Birds. https://www.allaboutbirds.org/guide/Ruddy_Duck.
[4] Audubon. “Ruddy Duck.” https://www.audubon.org/field-guide/bird/ruddy-duck.
[5] USFWS. “Species Assessment and Listing Priority Assignment Form: Black Scoter.” https://ecos.fws.gov/docs/species_assessments/black%20scoter.pdf.
[6] Ducks Unlimited. “Ruddy Duck.” https://www.ducks.org/hunting/waterfowl-id/ruddy-duck.