Red-breasted Merganser

Mergus serrator (Linnaeus, 1758) RM REBME 2210
Family: Anseriformes > Anatidae

Red-breasted Merganser, Allan Drewitt

One of three species of ‘sawbill’ that regularly occur in the UK, the Red-breasted Merganser can be told by its punk-style ‘hairdo’, glossy green in the male and rusty orange-red in the female.

The small breeding population is found mainly on Scottish lochs but pairs also use favoured waterbodies in western Britain and in Ireland.

Like many wildfowl, numbers grow during the winter and a wintering population of over 10,000 birds is not unusual. During the winter the Red-breasted Merganser is found almost exclusively on the sea, hunting small fish close to shore; Bird Atlas 2007–11 underlines that the species can be seen almost anywhere around our coast.


Red-breasted Merganser identification is often straightforward. The following article may help when identifying Red-breasted Merganser.

related video

Identifying Goosander and Red-breasted Merganser

Identifying the two large sawbills, Goosander and Red-breasted Merganser, can be pretty straight-forward when confronted with male birds. However, the females, or redheads as they are more often called, can be much more difficult. This video gives useful pointers on how to confidently tell them apart.


Listen to example recordings of the main vocalisations of Red-breasted Merganser, provided by xeno-canto contributors.


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Status and Trends

Population size and trends and patterns of distribution based on BTO surveys and atlases with data collected by BTO volunteers.


This species can be found on the following statutory and conservation listings and schedules.



Red-breasted Merganser was added to the list of species monitored by the RBBP in 2017, after the British breeding population was estimated at 1,565 (1,373–1,754) pairs (Humphreys et al. 2016). The main breeding strongholds are in Scotland (1,432 pairs), with smaller breeding concentrations also occurring in parts of northern England, north Wales and northern Ireland. Population trends are unclear but the breeding range has decreased by 28% since 1968–72 (Balmer et al. 2013).


In winter, Red-breasted Mergansers are widely distributed around the coast of Britain & Ireland, with distinct concentrations off western Scotland, the Northern Isles, northwest and southwest Ireland, north Wales and the Solent. In the breeding season they are more concentrated in the Scottish Isles, northwest Scotland, parts of north and west Ireland, northern England and northwest Wales.

Occupied 10-km squares in UK

European Distribution Map

European Breeding Bird Atlas 2


The breeding range of the Red-breasted Merganser has contracted by 28% since the 1968–72 Breeding Atlas, with losses concentrated in western Ireland, southwest Scotland and many inland parts of Scotland, particularly in the east and far north.

Change in occupied 10-km squares in the UK


Red-breasted Mergansers are present year-round, with wintering birds on many coasts and a localised breeder in the north.

Weekly occurence of Red-breasted Merganser from BirdTrack
Weekly occurrence patterns (shaded cells) and reporting rates (vertical bars) based on BirdTrack data. Reporting rates give the likelihood of encountering the species each week.


Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.


View a summary of recoveries in the Online Ringing Report.

Foreign locations of birds ringed or recovered in Britain & Ireland

Foreign locations of Red-breasted Merganser ringed or recovered in Britain & Ireland
Encountered in: Winter (Nov-Feb); Spring (Mar-Apr); Summer (May-Jul); Autumn (Aug-Oct)


Lifecycle and body size information about Red-breasted Merganser, including statistics on nesting, eggs and lifespan based on BTO ringing and nest recording data.



View number ringed each year in the Online Ringing Report


Feather measurements and photos on featherbase


For information in another language (where available) click on a linked name

Gaelic: Sìolta-dhearg
Welsh: Hwyaden Frongoch
Catalan: bec de serra mitjà
Czech: morcák prostrední
Danish: Toppet Skallesluger
Dutch: Middelste Zaagbek
Estonian: rohukoskel
Finnish: tukkakoskelo
French: Harle huppé
German: Mittelsäger
Hungarian: örvös bukó
Icelandic: Toppönd
Irish: Síolta Rua
Italian: Smergo minore
Latvian: garknabja gaura, melgale
Lithuanian: vidutinis danciasnapis
Norwegian: Siland
Polish: szlachar
Portuguese: merganso-de-poupa
Slovak: potápac prostredný
Slovenian: srednji žagar
Spanish: Serreta mediana
Swedish: småskrake


Interpretation and scientific publications about Red-breasted Merganser from BTO scientists.


Causes of change

The breeding population trend is unclear: range declines suggest that a population decline may have occurred but there are insufficient data to confirm this. Causes of the possible decline are also unknown, although there are concerns about the potential impact of piscivorous birds, including Red-breasted Merganser, on fisheries and licensed control of fish-eating birds is available to reduce potential economic losses (Humphreys et al. 2016).

Links to more information from

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