The common merganser, also known as the goosander in Europe, is a large duck species belonging to the genus Mergus. It is a migratory bird found across North America, Europe, and Asia. The common merganser lives along rivers, lakes, and coastlines, where it dives underwater to catch fish.
Some key facts about the common merganser:
- Scientific name: Mergus merganser
- Length: 50-65 cm
- Wingspan: 81-98 cm
- Weight: 0.9-1.8 kg
- Diet: Fish, aquatic insects, crustaceans
- Lifespan: Up to 13 years
In this article, we will provide a detailed physical description of the common merganser, discuss its habitat and range, breeding biology, diet and feeding behavior, lifespan and mortality, and conservation status.
Physical Description
The common merganser is a large, long-bodied duck with a slender, serrated bill. The adult male has a dark green head with a bushy crest, white neck collar, and red bill. Its back is black and its breast is a rich salmon-pink color. The female is smaller and has a grayish head and white chin.
Both sexes have bright red legs and feet. Their bodies are streamlined to allow for efficient diving and swimming underwater when catching prey. Some key physical features include:
- Large body size, one of the biggest ducks
- Long, slender serrated bill to help grasp slippery prey
- Strong legs and feet set far back on the body for diving
- Long tail helps provide thrust when swimming
- Dense plumage sheds water easily
Ducklings are covered in fuzzy down and have a patterned brown and beige appearance that helps camouflage them. Juveniles resemble adult females but have a gray bill and head. Males take 2-3 years to acquire their full adult plumage.
Habitat and Range
The common merganser has a circumpolar distribution across North America, Europe, and Asia. In North America, it breeds mainly in Canada and the northern United States, and migrates south to the southern and eastern U.S. for winter.
This species inhabits freshwater lakes, ponds, rivers, and estuaries. It prefers large bodies of water with plenty of fish and areas of dense emergent vegetation for nesting. During the winter, common mergansers are also found on coastlines and saltwater habitats.
Some key details about the habitat and range of common mergansers:
- Breed predominantly in forested areas near lakes, rivers, streams
- Nest in tree cavities, rock crevices, under shrubs, or in nest boxes
- Winter on large inland lakes, estuaries, sheltered coastlines
- Found across Canada, Alaska, northern U.S., migrates south to central/southern U.S.
- Also widely distributed across Europe and Asia in suitable habitats
The common merganser is generally not found in arid or treeless areas lacking suitable waterways for feeding and nesting. They have a widespread range but are most abundant in boreal forest habitats in Canada and Alaska.
Breeding Biology
Common mergansers begin breeding at 2-3 years of age. They are migratory and return to northern breeding grounds in late winter and early spring.
Males establish and defend breeding territories on lakes or rivers. They attract females through courtship displays on the water involving characteristic head-throwing motions and chasing.
Once paired, the female chooses the nest site, typically in a natural tree cavity or nest box within the male’s territory. The female lines the nest with down feathers plucked from her breast.
Clutch size is 6-12 eggs, which are incubated by the female for 28-35 days. The female carefully covers the eggs with nesting material when she leaves the nest to feed.
The young hatchlings are led by the female to water within 24 hours, where she cares for them until they fledge at around 70 days old. The male does not provide any parental care. The young are capable of diving and catching their own food after about 2-3 weeks.
- Breeding season May-July
- Males display to attract mates and defend territory
- Females select nest site, usually in natural cavity or nest box
- Clutch size 6-12 eggs, female incubates 28-35 days
- Young fledge in 8-10 weeks and dive for food after 2-3 weeks
Nest sites are reused and pairs may remain together for multiple breeding seasons. The female cares for and defends the young while they are vulnerable hatchlings.
Diet and Feeding
The common merganser is a piscivorous bird, meaning fish make up the majority of its diet. Its slender, serrated bill allows it to effectively grasp and hold slippery fish underwater as it swims and dives in pursuit of prey.
This species hunts for live fish in rivers, lakes, and shallow coastal waters. Some of the common fish consumed include:
- Minnows
- Suckers
- Sticklebacks
- Trout
- Salmon
- Eels
The common merganser needs to eat around 0.5 lbs of fish per day. It swallows most prey underwater but occasionally will surface with larger fish to swallow.
In addition to fish, these birds sometimes eat aquatic invertebrates like crustaceans, mollusks, and insects. Adults dive down and find food underwater while ducklings feed nearer the surface on smaller prey.
When breeding, females require extra protein and calcium to produce eggs. Males eat less during courtship and nesting periods. In winter, mergansers congregate where open water allows for fishing access.
Diving Ability
Common mergansers are expert divers and can reach depths up to 130 feet in search of fish! They can remain submerged for up to a minute.
Their streamlined bodies, toes with lobed flaps, and propulsive wingbeat under water allow them to swim and maneuver effectively on pursuit of fast fish. Their clear eyelid (nictitating membrane) protects the eyes while diving.
Lifespan and Mortality
In the wild, the average lifespan of the common merganser is 5-13 years. The oldest recorded individual was a female who lived to be over 17 years old.
This species faces predation mainly when young. Eggs and nestlings may be taken by minks, raccoons, snakes, and other birds. Ducklings additionally face threats from large predatory fish, snapping turtles, large gulls, and birds of prey.
Adult mergansers may occasionally be killed by foxes, lynxes, eagles, or other large predators, but their main cause of natural mortality is disease or accidents. Avian cholera outbreaks can kill significant numbers. Collisions with power lines or vehicles also cause some mortalities.
Human activities represent the greatest threats to common merganser populations today. Water pollution, oil spills, and human disturbance of nesting sites all negatively impact numbers. However, their widespread range and adaptability help them remain common and resilient overall.
Conservation Status
The common merganser has a large, healthy population and is considered a species of Least Concern by the IUCN Red List. Population trends remain stable without significant threats.
There are an estimated 1.7-3.1 million breeding common mergansers across North America, with the highest numbers in Canada and Alaska. There are also around 260,000 in Europe and 290,000 in Russia/Asia.
These birds are protected under the Migratory Bird Treaty Act in North America. Some specific conservation actions include:
- Protecting key breeding and wintering habitats
- Nest box programs to provide safe nesting sites
- Monitoring and reducing water pollution
- Public education about wetland conservation
By preserving wetland habitats and maintaining clean waterways, the common merganser’s future remains secure. They serve as an indicator of ecosystem health in their breeding and migration ranges.
Conclusion
In summary, the common merganser is a large, fish-eating duck capable of diving to great depths in search of prey. Their slender, serrated bill allows them to catch slippery fish, which are swallowed underwater or at the surface. These migratory waterfowl breed in northern forests and nest in cavities near water. The female alone cares for the young. Common mergansers are widespread and numerous throughout the northern parts of North America, Europe, and Asia. They congregate in relatively undisturbed wetlands and waterways with plenty of fish to prey on. Their diving abilities and varied diet allow common mergansers to thrive as a least concern species, as long as key breeding and wintering habitats are protected across their range.
| Scientific Name | Mergus merganser |
|---|---|
| Length | 50-65 cm |
| Wingspan | 81-98 cm |
| Weight | 0.9-1.8 kg |
| Diet | Fish, aquatic insects, crustaceans |
| Lifespan | Up to 13 years |
| Population | North America: 1.7-3.1 million Europe: 260,000 Russia/Asia: 290,000 |
| Conservation Status | Least Concern |
Related Questions
Where do common mergansers nest?
Common mergansers nest in cavities near water, either in natural tree hollows or artificial nest boxes. The female selects the nest site within the male’s breeding territory and lines it with down feathers.
How do common mergansers catch fish?
These diving ducks catch fish underwater during dives down to depths over 130 feet. They swim underwater and grasp fish with their long, slender bills which have sawtooth edges to help hold slippery prey.
Are common mergansers aggressive?
Males can be aggressive in defending breeding territories against intruding males. Females also may show aggression in defending the nest site or young. Overall though, common mergansers are not usually highly aggressive.
What threats do common mergansers face?
Pollution, habitat loss, human disturbance, and oil spills are some key threats. The young are also vulnerable to natural predators. However, their populations remain healthy overall.
How fast can common mergansers fly?
In flight, common mergansers can reach speeds of 55 mph. Their pointed wings and streamlined bodies make these diving ducks powerful and fast flyers during migration.
