Mergus Serrator Classification Essay


Taxonomy [top]


Scientific Name:Mergus serrator Linnaeus, 1758
Regional Assessments:


Common Name(s):
EnglishRed-breasted Merganser
Taxonomic Source(s):Cramp, S. and Simmons, K.E.L. (eds). 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.

Assessment Information [top]

Red List Category & Criteria: Near Threatened (Regional assessment) ver 3.1
Year Published:2015
Date Assessed:2015-03-31
Assessor(s):BirdLife International
Reviewer(s):Symes, A.
Facilitator/Compiler(s):Ashpole, J, Burfield, I., Ieronymidou, C., Pople, R., Wheatley, H. & Wright, L
European regional assessment: Near Threatened (NT)
EU27 regional assessment: Near Threatened (NT)

Within Europe this seaduck has undergone moderately rapid declines and is classified as Near Threatened.

In the EU27 declines have been more rapid and it qualifies as Vulnerable (A2abcde+3bcde+4abcde).

Geographic Range [top]

Range Description:The species breeds in Greenland (to Denmark), Iceland, and much of northern Eurasia south to the United Kingdom and parts of eastern Europe. Its wintering grounds expand its range to include areas of central Europe and the Mediterranean basin and the Black Sea (Carboneras and Kirwan 2014).
Countries occurrence:


Albania; Armenia; Austria; Azerbaijan; Belarus; Belgium; Bosnia and Herzegovina; Bulgaria; Croatia; Cyprus; Czech Republic; Denmark; Estonia; Faroe Islands; Finland; France; Germany; Greece; Greenland; Hungary; Iceland; Ireland; Italy; Latvia; Liechtenstein; Lithuania; Macedonia, the former Yugoslav Republic of; Malta; Moldova; Montenegro; Netherlands; Norway; Poland; Portugal; Romania; Russian Federation (European Russia); Serbia; Slovakia; Slovenia; Spain (Canary Is. - Vagrant); Sweden; Switzerland; Turkey; Ukraine; United Kingdom


Gibraltar; Luxembourg; Svalbard and Jan Mayen
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:2510000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Range Map:

Population [top]

Population:The European population is estimated at 70,100-120,000 pairs, which equates to 140,000-240,000 mature individuals. The population in the EU27 is estimated at 48,600-68,600 pairs, which equates to 97,200-137,000 mature individuals. For details of national estimates, see the supplementary material.

Trend Justification:  In Europe the population size is estimated to be decreasing at a rate approaching 30% in 21.9 years (three generations). In the EU27 the population size is estimated to be decreasing by 30-49% in the same period. For details of national estimates, see attached PDF.
Current Population Trend:Decreasing
Additional data:
Number of mature individuals:140000-240000,181000Continuing decline of mature individuals:Yes
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:The species breeds along the wooded shorelines (Kear 2005) of deep lakes, small rivers and streams (Carboneras and Kirwan 2014) with moderate currents, in the tundra, boreal and temperate forest zones, as well as on more saline waters such as sheltered shallow bays, inlets, straits or estuaries with sandy rather than muddy substrates. It shows a preference for narrow channels rather than open expanses of water, with islands or islets and spits, projecting rocks or grassy banks (Snow and Perrins 1998). The majority of the species winters at sea, frequenting both inshore and offshore waters, estuaries, bays and brackish lagoons (Carboneras and Kirwan 2014) but showing a preference for clear, shallow waters not affected by heavy wave action (Johnsgard 1978). It will also utilise large freshwater lakes on passage (Madge and Burn 1988). It breeds from April or May (later in northern populations) (Kear 2005). The nest is constructed within 25 m of water in a variety of locations such as natural cavities on the ground, burrows (Kear 2005, Carboneras and Kirwan 2014), under boulders (Madge and Burn 1988), amongst tree or scrub roots (Snow and Perrins 1998), in tree cavities, artificial nest boxes (Madge and Burn 1988), amongst reeds or on floating reed mats (Flint et al. 1984). Clutch size is normally eight to ten. Its diet consists predominantly of small, shoaling marine or freshwater fish, as well as small amounts of plant material and aquatic invertebrates. This species is fully migratory (Carboneras and Kirwan 2014) although in temperate regions it only undertakes short distance movements to nearby coasts (Scott and Rose 1996)
Systems:Terrestrial; Freshwater; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):7.3
Movement patterns:Full Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): The species is subject to persecution and may be shot by anglers and fish-farmers who accuse it of depleting fish stocks. It is also threatened by accidental entanglement and drowning in fishing nets (Kear 2005). Alterations to its breeding habitats by dam construction and deforestation, and habitat degradation from water pollution are other major threats to the species (Carboneras and Kirwan 2014). It is also susceptible to avian influenza so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006). The species is hunted in Denmark (Bregnballe et al. 2006), although it may not be a popular game species (Kear 2005). The eggs of the species also used to be (and possibly still are) harvested in Iceland (Gudmundsson 1979).

Conservation Actions [top]

Conservation Actions:Conservation Actions Underway
CMS Appendix II. EU Birds Directive Annex II. The breeding density of this species increased on islands in the outer archipelago of south-west Finland as a result of feral American Mink (Neovison vison) removal (Nordstrom et al. 2002).

Conservation Actions Proposed
The erection of nest boxes may encourage the use of local areas by this species. Strict legislation on petroleum drilling and transport should be enforced and measures to reduce bycatch implemented and enforced. Important areas should be protected from drainage and other habitat modifications. Research into the impact this species has on fish stocks and ways to minimise conflict should be established.

Mergus is the genus of the typical mergansers, fish-eating ducks in the subfamily Anatinae. The genus name is a Latin word used by Pliny and other Roman authors to refer to an unspecified waterbird.[1][2]

The hooded merganser, often termed Mergus cucullatus, is not of this genus but closely related. The other "aberrant" merganser, the smew (Mergellus albellus), is phylogenetically closer to goldeneyes (Bucephala).

Although they are seaducks, most of the mergansers prefer riverine habitats, with only the red-breasted merganser being common at sea. These large fish-eaters typically have black-and-white, brown and/or green hues in their plumage, and most have somewhat shaggy crests. All have serrated edges to their long and thin bills that help them grip their prey. Along with the smew and hooded merganser, they are therefore often known as "sawbills". The goldeneyes, on the other hand, feed mainly on mollusks, and therefore have a more typical duck-bill.[3]

Mergus are also classified as "divers" because they go completely under-water in looking for food. In other traits, however, the genera Mergus, Lophodytes, Mergellus, and Bucephala are very similar; uniquely among all Anseriformes, they do not have notches at the hind margin of their sternum, but holes surrounded by bone.[4]


Some fossil members of this genus have been described:

The Early Oligocenebooby"Sula" ronzoni was at first mistakenly believed to be a typical merganser.[6] A Late Serravallian (12–13 million years ago) fossil sometimes attributed to Mergus, found in the Sajóvölgyi Formation of Mátraszőlős, Hungary, probably belongs to Mergellus.[7] The affiliations of the mysterious "Anas" albae from the Messinian (c. 5–7 million years ago) of Hungary are undetermined; it was initially believed to be a typical merganser too.[8]



Wikimedia Commons has media related to Mergus.
  1. ^Jobling, James A (2010). The Helm Dictionary of Scientific Bird Names. London: Christopher Helm. p. 251. ISBN 978-1-4081-2501-4. 
  2. ^Etymology: Latinmergus, a catch-all term for sea-going birds: Arnott, W.G. (1964). "Notes on Gavia and Mergvs in Latin Authors". Classical Quarterly (New Series). 14 (2): 249–262. doi:10.1017/S0009838800023806. JSTOR 637729. 
  3. ^"Common Goldeneye". Seattle Audubon Society. Retrieved 18 April 2014. 
  4. ^Livezey, Bradley C. (1986). "A phylogenetic analysis of recent anseriform genera using morphological characters"(PDF). Auk. 103 (4): 737–754. 
  5. ^Mlíkovský, Jirí (2002a). "Early Pleistocene birds of Stránská skála, Czech Republic: 2. Absolon's cave"(PDF). Sylvia. 38: 19–28. 
  6. ^Mlíkovský (2002b): p. 264
  7. ^Gál, Erika; Hír, János; Kessler, Eugén & Kókay, József (1998–99). "Középsõ-miocén õsmaradványok, a Mátraszõlõs, Rákóczi-kápolna alatti útbevágásból. I. A Mátraszõlõs 1. lelõhely [Middle Miocene fossils from the sections at the Rákóczi chapel at Mátraszőlős. Locality Mátraszõlõs I.]"(PDF). Folia Historico Naturalia Musei Matraensis (in Hungarian and English). 23: 33–78. 
  8. ^Mlíkovský (2002b): p. 124


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