Red-Breasted Merganser Diet and Size: Feeding Habits, Predators, and Measurements
The Red-Breasted Merganser (Mergus serrator) is a fascinating diving duck known for its distinctive appearance and remarkable fishing abilities.
This streamlined waterfowl, often called the “sawbill” due to its serrated bill, holds an impressive record as the fastest duck species ever recorded, capable of reaching speeds up to 100 mph during flight.
In this article, let’s have a closer look into their feeding habits, predators, conservation status, and measurements!
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The Dietary Habits Of The Red-Breasted Merganser
Red-Breasted Mergansers are highly specialised aquatic predators, equipped with unique adaptations for underwater hunting.
What Does A Red-Breasted Merganser Eat?
Red-Breasted Mergansers are predominantly piscivorous, meaning fish make up the majority of their diet. Their serrated bills are perfectly adapted for catching and holding slippery prey underwater.
These skilled hunters primarily feed on small fish species up to 10 cm in length. While fish constitute their main diet, they also consume aquatic insects, worms, crustaceans, and small amphibians when available.
During winter months, they often form cooperative hunting groups, working together to herd fish into shallow waters where they become easier to catch. This social hunting behaviour demonstrates their remarkable intelligence and adaptability.
What To Feed A Baby Red-Breasted Merganser?
Baby Red-Breasted Mergansers, known as ducklings, are precocial and can feed themselves within hours of hatching. The mother leads them to suitable feeding areas where they initially catch small aquatic insects and larvae.
As they grow and develop their diving skills, young mergansers gradually transition to catching small fish. Their serrated bills develop early, enabling them to handle increasingly larger prey as they mature.
Breeding Habits Of Red-Breasted Mergansers
Red-Breasted Mergansers have fascinating breeding patterns that typically begin in the late winter.
Do Red-Breasted Mergansers Mate For Life?
Red-Breasted Mergansers do not mate for life but form new pair bonds each breeding season.
Their courtship typically begins in late winter, featuring elaborate displays where males perform head-throwing movements and make distinctive cat-like calling sounds to attract females.
These birds nest in sheltered locations on the ground, often hidden among dense vegetation near water bodies. The female constructs the nest alone, lining it with down feathers plucked from her breast.
She typically lays 8 to 10 olive-buff coloured eggs and handles all incubation duties, which last approximately 30 to 32 days.
The Size & Weight Of Red-Breasted Mergansers
Red-Breasted Mergansers are medium-sized diving ducks with distinctive proportions that set them apart from other waterfowl.
How Much Does A Red-Breasted Merganser Weigh?
Adult Red-Breasted Mergansers typically weigh between 900 to 1,350 grams. Males are generally heavier than females, showing sexual dimorphism typical of many duck species.
Their weight can fluctuate seasonally, with birds being heaviest before migration and during the breeding season when food is abundant.
How Big Is A Red-Breasted Merganser?
Red-Breasted Mergansers measure between 52 to 58 centimetres in length, with a wingspan ranging from 70 to 86 centimetres. Their slender, streamlined body shape is perfectly adapted for their diving lifestyle.
These measurements make them slightly smaller than their close relative, the Goosander, but their sleek build and distinctive spiky crest make them easily recognisable.
Are Red-Breasted Mergansers Under Threat?
Red-Breasted Mergansers are currently Amber-listed in the UK Birds of Conservation Concern.
Globally, they are classified as Least Concern on the IUCN Red List of Threatened Species.
What Eats A Red-Breasted Merganser?
Adult Red-Breasted Mergansers face predation from large birds of prey such as White-tailed Eagles and Peregrine Falcons. Their eggs and ducklings are vulnerable to various predators including foxes, mink, and large gulls.
Their nesting strategy of choosing well-concealed ground sites helps protect against predation, though it doesn’t eliminate the risk entirely.
Where Can I See Red-Breasted Mergansers In The UK?
Red-Breasted Mergansers can be observed along most of the UK coastline, particularly during winter months. They are more commonly seen around Scotland’s coastline and islands, where many pairs remain to breed.
Excellent viewing locations include the sea lochs of western Scotland, the Moray Firth, and various estuaries around the British coast. During winter, they can also be spotted in sheltered bays and harbours, where they often form small fishing groups.
In the breeding season, some pairs move inland to freshwater lakes and rivers, though this is less common than in their cousin, the Goosander.
SEE ALSO: Red-Breasted Merganser Life Cycle: Nest Building To Fledging (and everything in between)
Frequently Asked Questions
Males have distinctive dark green heads with a spiky crest, white neck ring, and rusty-coloured breast band, while females have a rusty-brown head and greyish body. This difference is most pronounced during the breeding season.
Red-Breasted Mergansers can be seen year-round in the UK, but they are most numerous during winter months when birds from northern Europe join our resident population.
Yes, many Red-Breasted Mergansers migrate. While some UK birds are resident, others move south from their northern breeding grounds for winter, and our winter population is boosted by birds from northern Europe.
