Greater Scaup: Complete Guide to ID, Diet, Habitat & Behavior (2025)

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You’ll recognize a greater scaup by its distinctive rounded head shape and striking coloration.

Males sport glossy black heads with green sheens, bright white sides, and dark backs, while females display rich brown plumage throughout.

These diving ducks are built like underwater torpedoes—they’ll disappear beneath the surface for 20-30 seconds, hunting mollusks and aquatic vegetation at depths up to 20 feet.

During winter, you’ll find massive rafts of thousands gathering on large lakes and coastal bays across North America.

Their yellow eyes and blue-gray bills with black nail tips make identification straightforward, especially when compared to their smaller cousin, the lesser scaup.

The way they form these enormous floating communities reveals fascinating social behaviors that most waterfowl enthusiasts never witness.

Greater Scaup Overview

You’ll easily recognize the Greater Scaup as a medium-sized diving duck with its distinctive rounded head and broad blue-gray bill.

This northern waterfowl ranges from 15-20 inches long and displays striking black, white, and gray plumage patterns that vary between males and females, showcasing its unique plumage.

Physical Description

You’ll immediately notice the Greater Scaup’s distinctive features when spotting this medium-sized diving duck.

Males showcase striking black and white male plumage with a blue-gray beak, while females display rich brown female plumage.

Their smoothly rounded head shape distinguishes them from peaked heads of similar species, and their short, square-tipped tail length creates a compact silhouette during flight.

Their overall appearance, including the blue-gray beak, contributes to their unique identity among diving ducks.

Identification Features

You’ll recognize greater scaup through several distinctive features that set Aythya marila apart from similar waterfowl.

Look for their smoothly rounded head shape without peaked crowns, plus broad blue-gray beak colors that appear larger than related species.

Males display striking black and white feather patterns with greenish head sheens, while prominent white wing stripes become visible during flight.

Their square-tipped tail features help confirm proper bird identification in the field, with broad blue-gray beak colors being a notable characteristic.

Size and Color Variations

You’ll find greater scaup (Aythya marila) display remarkable size and color variations between sexes and seasons.

These medium-sized diving ducks measure 15-20 inches with distinctive plumage changes throughout the year.

Key Size and Color Variations:

• Male breeding plumage: Black head with green sheen, gray back, white sides
• Female coloration: Overall brown with white belly patch and bill base
• Size differences: 18-inch length, 28-inch wingspan, 2.3-pound average weight
• Seasonal plumage changes: Males lose bright colors in non-breeding season
• Beak variations: Broad blue-gray bills distinguish them from similar species

Greater Scaup Habitat

You’ll find Greater Scaup in dramatically different environments throughout the year, from Arctic tundra lakes where they breed to coastal bays where they spend winter months.

From frozen Arctic lakes to warm coastal waters, these adaptable ducks master both worlds effortlessly.

Understanding their habitat preferences helps you predict where to spot these diving ducks during different seasons and migration periods, which is crucial for effective spotting.

Breeding Habitats

You’ll discover Greater Scaup (Aythya marila) in tundra regions and marshlands across the Arctic Circle.

These wetland birds choose breeding grounds near large freshwater habitats, particularly marshy lowland areas and northern boreal forest edges.

About 75% of North American scaup breeding occurs in Alaska’s expansive lakes. Scaup habitat includes small islands and shorelines where nesting sites offer protection and access to food sources essential for successful reproduction.

Winter Habitats

When winter arrives, you’ll find Greater Scaup trading Arctic tundra for warmer coastal bays and marine environments.

These wetland birds prefer saltwater habitats like estuaries and tidal waters over freshwater habitats.

The Greater Scaup’s population decline is linked to coastal pollution issues, and they favor exposed, windier locations compared to their Lesser cousins, with flocks gathering in hundreds across Atlantic and Pacific coastlines.

Migration Patterns

You’ll observe Greater Scaup following predictable flyway routes during their seasonal movements between Arctic breeding grounds and temperate wintering areas.

These migratory birds typically begin their southern journey in late summer, with peak migration timing occurring from September through November along major North American and Eurasian corridors.

• Atlantic and Pacific Flyway Routes – North American populations use coastal corridors for long-distance travel
• Stopover Sites – Large flocks gather at key lakes and bays to refuel during migration
• Flight Patterns – Travel in loose formations at moderate altitudes, often following shorelines
• Seasonal Movements – Spring migration occurs March through May, returning to northern breeding territories
• Scaup Migration Timing – Weather patterns and food availability influence departure and arrival dates

Understanding the complex bird migration patterns is essential for conservation efforts and protecting these species.

Greater Scaup Characteristics

You’ll easily recognize Greater Scaup by their distinctive physical features that set them apart from similar diving ducks.

Understanding these key characteristics will help you confidently identify males, females, and juveniles in the field, which is crucial for confidently distinguishing between different species.

Male and Female Differences

Males and females show striking sex dimorphism during breeding season. Breeding males display glossy green-black heads and contrasting white sides, while females feature brown bodies with distinctive white facial patches.

Plumage variation becomes most pronounced in spring, helping you distinguish between sexes easily. Understanding the scaup species differences is essential for accurate identification of Greater Scaup.

Feature	Males	Females
Head Color	Glossy green-black	Dark brown
Body Pattern	White sides, black breast	Brown overall
Weight Range	860g average	730-800g

Nonbreeding males resemble females but retain subtle iridescence. Greater Scaup plumage differences extend beyond feather color – males average larger at 44-51cm versus females’ 40-47cm length.

Beak Shape and Size

The Greater Scaup’s distinctive bluegray beak serves as a key identification marker.

You’ll notice their bill length is markedly broader and larger compared to similar diving ducks.

This mouth size advantage helps them sift through sediment effectively.

The beak structure remains consistently robust across both sexes, though males may show slightly more pronounced dimensions.

Their nose shape appears flattened and wide, perfectly adapted for their underwater feeding lifestyle, with a beak that is robust.

Head and Feather Coloration

Looking at a male Greater Scaup’s head reveals a stunning black surface with gloss effects creating greenish highlights—never purple like its Lesser cousin.

Feather patterns show smooth, rounded head shapes without peaks, while females display rich brown head colors with distinctive white patches at their beak base.

Wing patterns feature broad white stripes during flight, and plumage variations include paler face markings in winter plumage.

Greater Scaup Feeding Habits

You’ll discover that Greater Scaup are opportunistic feeders with a diet that changes dramatically throughout the year.

These skilled diving ducks can plunge up to 6 meters underwater to hunt for mollusks, crustaceans, and aquatic insects on lake and bay bottoms, which showcases their diving abilities.

Diet Composition

You’ll find that mollusk intake forms the cornerstone of the scaup diet, with clams and mussels comprising up to 45% of their meals during migration.

These diving ducks also consume aquatic plants, crustaceans like amphipods, insect larvae, and fish eggs opportunistically.

Their bird diet shifts seasonally—more plant matter in winter, invertebrates during breeding.

The scaup’s food sources include a variety of scaup food that are essential for their survival and comprise a significant part of their diet.

Foraging Techniques

When you watch Greater Scaup in action, you’ll notice their impressive diving methods that showcase nature’s engineering at its finest.

These underwater acrobats dive deeper than most ducks dare, turning lakes into their personal hunting grounds.

These skilled aquatic feeders employ multiple foraging strategies to access food sources below the surface.

The use of proper diving gear, including equipment for safe diving practices, is essential for humans to explore such underwater environments.

Diving Methods used by Greater Scaup:

• Deep dives – Plunge up to 20 feet underwater using powerful leg strokes
• Bottom sifting – Use broad bills to filter sediment for mollusks and crustaceans
• Underwater swimming – Navigate submerged areas to hunt aquatic insects
• Surface dabbling – Quick shallow feeding for floating food particles
• Nocturnal foraging – Feed actively during nighttime hours following tidal patterns

Food Sources and Availability

Whatever the season brings, you’ll discover that Greater Scaup adapt their mollusk diet and plant matter consumption to available resources.

Their crustacean feeding intensifies during breeding season, while aquatic insects become vital protein sources.

Winter brings increased seed consumption from aquatic plants, and these diving ducks exploit everything from zebra mussels to pondweed, showcasing remarkable dietary flexibility that guarantees survival across diverse habitats.

Understanding the species comparison details is essential for recognizing the unique characteristics of Greater Scaup.

Greater Scaup Reproduction

You’ll find Greater Scaup reproduction follows a fascinating seasonal pattern that begins during their spring migration north.

These diving ducks establish breeding pairs and select nesting sites in the Arctic tundra and boreal regions where they’ll raise their next generation, which is a crucial part of their reproduction.

Breeding and Nesting

Pairs form during spring migration as these ducks return to their breeding grounds in Alaska and northern regions.

You’ll find them selecting nest sites on small islands or shorelines near large lakes, where females create shallow depressions lined with grass and down.

These ground-based nesting locations offer protection while remaining close to abundant food sources for successful brood rearing.

Understanding the species identification factors is essential for recognizing Greater Scaup in their natural habitats, which involves considering complete concepts.

Egg Laying and Incubation

Female Greater Scaup create shallow ground nests near water’s edge during late spring.

These dedicated mothers lay 6-11 olive-buff eggs over several days, with each egg formation taking roughly 24 hours.

The incubation period lasts 24-28 days, during which females rarely leave their nesting sites except for brief feeding breaks.

The use of nesting box designs can help improve nesting success in certain environments.

• Egg Formation: Females produce one egg daily until clutch completion, typically containing 7-9 eggs
• Incubation Period: Constant brooding for nearly four weeks guarantees proper embryo development and temperature control
• Nesting Habits: Ground nests lined with grass and down provide insulation in tundra environments
• Hatching Rates: Successful fertilization process yields high hatching success when predators don’t interfere with nesting

Lifespan and Survival Rates

Greater scaup typically live 10-15 years, though maximum recorded lifespan reaches 20 years.

Annual survival rates hover around 81% for adults, but duckling survival drops to just 37.5% within 30 days.

Population trends show concerning decline—North American numbers fell to 3.6 million by 2022.

Major death causes include fishing net drowning, pollution, and predation.

Conservation efforts target these mortality rates through habitat protection. Understanding the bird diving habits is essential for developing effective conservation strategies.

Frequently Asked Questions (FAQs)