The red-breasted merganser (Mergus serrator) is one of only
two species of sawbill duck (the other being the goosander) that breeds in the
British Isles. The red-breasted merganser has a long history of residence in
Scotland and Ireland. However, since about 1950 they have spread into England, breeding
as far south as Derbyshire and also into Wales.
Red-breasted mergansers grow to around 23 inches (58 cm) in
length. Adult males have dark green heads and reddish-brown breasts and necks.
The head has a double crest. Females are brown on the head and neck, the
colouring merging into the breast. Their white wing patches are most noticeable
in flight.
Flight is fast and direct, with the neck and body
outstretched to produce a long, narrow shape.
The term ‘sawbill’ refers to the finely serrated cutting
edges on the bills that enable red-breasted mergansers to grasp slippery fish.
When fishing, they often swim with the head under water before diving to catch
their prey.
Red-breasted mergansers have suffered persecution in the
past due to their liking for young trout and salmon. However, they also eat
species including eels, perch and pike which prey on the eggs and young of
salmon and trout.
The nest is a shallow depression in the ground, lined with
grass, leaves and down, that is sited near a river or lake and often in thick
vegetation which makes it difficult for a predator to find. From late April to
early July the female lays and incubates 8 to 10 eggs that take a month to
hatch. When she leaves the nest to feed, she camouflages the eggs with down.
When hatched, the ducklings are attended to by the female on her own. They can
fly around two months after they hatch. Only one brood is reared each year.
© John Welford
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