Mobile bird identification
Bird Field Guide

Red-breasted Merganser

Mergus serrator
Order: Anseriformes

Family: Anatidae

Genus:  Mergus

Species: M. serrator
Note the very distinctive dark head, red bill and crest. From a distance the Red-breasted Merganser can look like a black and white bird. The Male Goosander in Winter is a similar looking bird but he lacks the red eye and crest and has white flanks.
The Male Red-breasted Merganser in Winter has a green-black head with a wispy crest. Its bill is long, slim, red and slightly upturned. The body of the bird has a broad white strip down the back and it has grey flanks and a black back.
Adult Male Winter
Distribution
Winter visitor
Resident bird
Resident
Summer
Passage Migrant
Passage
Winter
Summer visitor
Red-breasted Merganser distribution
General distribution:
Breeds In Northern UK and the North of Europe. Generally moves South to Winter but some birds remain around breeding areas.
Habitat:
The Red-breasted Merganser breeds near rivers or next to the sea. When not breeding it favours sheltered estuaries and sea lochs.
Notes:
During the winter the Red-breasted Merganser is a social bird, most often seen in small, same sex groups. When feeding it will often dip its head below the water to look for food before diving.
A Male and Female bird in flight, note the very bright and distinctive white wing patches.
Thanks to:https://www.flickr.com/photos/themadbirdlady/ (Modified)
Identifying a Male Red-breasted Merganser

*Long, red, thin turned up bill

White bands down back

*Dark head, wispy crest
Thanks to:https://www.flickr.com/photos/ze;
* key ID points
Adult Female

Grey flanks

*White collar

Identifying a Female Red-breasted Merganser
Male and Female Merganser flying
Female Red-breasted Merganser, note how she looks below the surface for food before diving. This is a habit which can help with identification.
Wildfowl (Ducks)
Male Merganser in Winter
Thanks to:https://www.flickr.com/photos/acrylicartist/(Modified)

*Red eye

Adult Male Summer (Eclipse)
Male Merganser in Summer
The Male Red-breasted Merganser in Summer can look frustratingly like the Female, he has a bolder white wing patch, more substantial crest and a darker face. His flanks are also greyer than the female.
Thanks to:https://www.flickr.com/photos/zenbikescience/ (Modified)
The Female Red-breasted Merganser has a brownish-grey body and a chestnut-brown head, her bill is red, thin and slightly upturned. Her eye is red and she has a small white wing patch. Note that she lacks a defined white collar/throat on the neck like the very similar Female Goosander.
Thanks to:Bryan's bird photography
Identifying a Female Red-breasted Merganser
Thanks to:https://www.flickr.com/photos/79452129@N02/ (Modified)
The Female Red-breasted Merganser's body colour can vary from dark brown, almost black, to light grey like this bird. This can also be very much dependent upon the lighting conditions that the bird is viewed in.