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Common murre

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The common murre or common guillemot (Uria aalge) is a large auk. It has a circumpolar distribution, occurring in low-Arctic and boreal waters in the North Atlantic and North Pacific. It spends most of its time at sea, only coming to land to breed on rocky cliff shores or islands.

Common murres are fast in direct flight but are not very agile. They are highly mobile underwater using their wings to 'fly' through the water column, where they typically dive to depths of Template:Convert. Depths of up to Template:Convert have been recorded.

Common murres breed in colonies at high densities. Nesting pairs may be in bodily contact with their neighbours. They make no nest; their single egg is incubated between the adult's feet on a bare rock ledge on a cliff face. Eggs hatch after ~30 days incubation. The chick is born downy and can regulate its body temperature after 10 days. Some 20 days after hatching, the chick leaves its nesting ledge and heads for the sea, unable to fly, but gliding for some distance with fluttering wings, accompanied by its male parent. Male guillemots spend more time diving, and dive more deeply than females during this time. Chicks are capable of diving as soon as they hit the water. The female stays at the nest site for some 14 days after the chick has left.

Both male and female common murres moult after breeding and become flightless for 1–2 months. Some populations have short migration distances, instead remaining close to the breeding site year-round. Such populations return to the nest site from autumn onwards. Adult birds balance their energetic budgets during the winter by reducing the time that they spend flying and are able to forage nocturnally.

TaxonomyEdit

The common murre was formally described and illustrated in 1763 by the Danish bishop Erik Pontoppidan under the binomial name Colymbus aalge.<ref>Template:Cite book</ref> The type locality is Iceland.<ref>Template:Cite book</ref> The species is now placed together with the thick-billed murre in the genus Uria that was described in 1760 by the French zoologist Mathurin Jacques Brisson.<ref name=ioc>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> The genus name is from Ancient Greek ouria, a waterbird mentioned by Athenaeus. The specific epithet aalge is an old Danish word for an auk.<ref>Template:Cite book</ref>

The auks are a family of seabirds related to the gulls and terns which contains several genera. The common murre is placed in the guillemot (murre) genus Uria (Brisson, 1760), which it shares with the thick-billed murre or Brunnich's guillemot, U. lomvia. These species, together with the razorbill, little auk and the extinct great auk make up the tribe Alcini. This arrangement was originally based on analyses of auk morphology and ecology.<ref name = strauch1985>Strauch (1985)</ref>

The official common name for this species is Common Murre according to the IOC World Bird List, Version 11.2.<ref name=ioc/> while Common Guillemot is used in the UK,<ref>Template:Cite journal</ref> Ireland,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and often elsewhere in Europe where English is used as a second language.<ref>see e.g. the English name column of the Finnish Bird List {{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Five subspecies are now recognised:<ref name=ioc/>

EtymologyEdit

The spelling guillemot is of French origin, first attested by Pierre Belon in 1555, but derived from Old (11th century) French willelm, and matched by English variants willock (attested 1631), willick, will and wilkie, all from forms of the name William, cf. Template:Langx, but ultimately onomatopoeic from the loud, high-pitched "will, willem" begging calls of the newly fledged young of the common guillemot.<ref name="Lockwood">Template:Cite book</ref> The American name murre, also known from England (particularly Cornwall) from the 17th century, is by contrast, onomatopoeic of the growling call of adult common guillemots.<ref name="Lockwood"/><ref>External audio: growling "murre" calls of adult, and "willem" calls of young, common guillemots, at xeno-canto</ref>

DescriptionEdit

The common murre is Template:Convert in length with a Template:Convert wingspan.<ref name = mullarney1999>Mullarney et al. (1999)</ref> Male and female are indistinguishable in the field and weight ranges between Template:Convert in the south of their range and Template:Convert in the north.<ref name = harris1985 >Harris & Birkhead (1985)</ref> A weight range of Template:Convert has been reported.<ref name = "CRC">CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), Template:ISBN.</ref> In breeding plumage, the nominate subspecies U. a. aalge is black on the head, back and wings, and has white underparts. It has a thin dark pointed bill and a small rounded black tail. After the post-breeding moult, the face is white with a dark spur behind the eye, and there are often dark streaks on the flanks.<ref name = mullarney1999 /> Birds of the subspecies U. a. albionis are dark brown rather than black, most obviously so in colonies in southern Britain. The legs and the bill are dark grey. Occasionally, adults have been seen with yellow-grey legs. In May 2008, an aberrant adult was photographed with a bright yellow bill.<ref>Blamire (2008)</ref>

The adults moult into breeding plumage in December–February, even starting as early as November in U. a. albionis, and back into winter plumage soon after leaving the breeding colonies in July to August. The plumage of first winter birds is the same as the adult winter plumage. However, their moult into first summer plumage occurs later in the year than in adults. First year birds often remain in winter plumage as late as May, and their first summer plumage usually retains some white feathers around the throat.<ref name = mullarney1999 />

Some individuals in the North Atlantic, known as "bridled guillemots", have a white ring around the eye extending back as a white line. This is not a distinct subspecies, but a polymorphism that becomes more common the farther north the birds breed.<ref name = hbw>Nettleship (1996)</ref>

The chicks are downy with blackish feathers on top and white below. By 12 days old, contour feathers are well developed in areas except for the head. At 15 days, facial feathers show the dark eyestripe against the white throat and cheek.<ref name=mahoney1981/> They jump from the breeding cliffs at 20–21 days old, long before being fully fledged, and are cared for by the male parent at sea.<ref name = mullarney1999 />

The common murre has a variety of calls, including a soft purring noise, but the main call of the adults, often deafening at large colonies, is a growling "murrrr"; the chicks have a food-begging call, a high-pitched whistle "willee", with considerable carrying power.

  • Winter uria aalge.jpg

    Adult in winter plumage, Germany

  • Guillemot (Uria aalge) in flight.jpg

    in flight off Skomer Island

  • Guillemot (Uria aalge) mature, on water.jpg

    Mature 'bridled' bird (white eye ring)

FlightEdit

The common murre flies with fast wing beats and has a flight speed of Template:Convert.<ref name=vaughn1937>Vaughn (1937)</ref> Groups of birds are often seen flying together in a line just above the sea surface.<ref name = mullarney1999 /> However, a high wing loading of 2 g/cm2<ref name=livezey1988>Livezey (1988)</ref> means that this species is not very agile and take-off is difficult.<ref name=bedard1985>Bédard (1985)</ref> Common murres become flightless for 45–60 days while moulting their primary feathers.<ref name=birkheadtaylor1977>Birkhead & Taylor (1977)</ref> The sound of the wing beats of the murres are often described as similar to a helicopter.

DivingEdit

File:Lomvia troile 53.jpg
Skeleton

The common murre is a pursuit-diver that forages for food by swimming underwater using its wings for propulsion. Dives usually last less than one minute, but the bird swims underwater for distances of over Template:Convert on a regular basis. Diving depths up to Template:Convert have been recorded,<ref name ="Piatt"/> and birds can remain underwater for a couple of minutes.

Distribution and habitatEdit

Template:Update section The breeding habitat is islands, rocky shores, cliffs and sea stacks. The population is large, perhaps 7.3 million breeding pairs <ref name = mitchell2004>Mitchell et al. (2004)</ref> or 18 million individuals.<ref name="iucn status 12 November 2021" /> It had been stable, but in 2016 a massive die-off of the birds in the northeast Pacific was reported. The birds seem emaciated and starving; no etiology has been found.<ref>A massive die-off</ref> In general, potential threats include excessive hunting (legal in Newfoundland), pollution and oil spills. Cape Meares, Oregon is home to one of the most populous colonies of nesting common murres on the North American continent.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Some birds are permanent residents; northern birds migrate south to open waters near New England, southern California, Japan, Korea and the western Mediterranean. UK populations are generally distributed near their breeding colonies year-round, but have been found to make long-distance migrations as far north as the Barents Sea.<ref name="Buckingham et al. 2022">Template:Cite journal</ref> Common murres rest on the water in the winter and this may have consequences for their metabolism. In the black-legged kittiwake (which shares this winter habit) resting metabolism is 40% higher on water than it is in air.<ref name = humphreys2007>Humphreys et al. (2007)</ref>

A marine heat wave killed off half the murre population in Alaska between 2014 and 2016, and as of 2024 the species has yet to recover.<ref>Template:Cite news</ref>

Behavior and ecologyEdit

Food and feedingEdit

The common murre can venture far from its breeding grounds to forage; distances of Template:Convert and more are often observed<ref name = lilliendahletal2003>Lilliendahl et al. (2003)</ref> though if sufficient food is available closer by, birds only travel much shorter distances. The common murre mainly eats small schooling forage fish Template:Convert long or less, such as polar cod, capelin, sand lances, sprats, sandeels, Atlantic cod and Atlantic herring. Capelin and sand lances are favourite food, but what the main prey is at any one time depends much on what is available in quantity.<ref name = lilliendahletal2003 /> It also eats some molluscs, marine worms, squid, and crustaceans such as amphipods. It consumes Template:Convert of food in a day on average. It is often seen carrying fish in its bill with the tail hanging out.<ref name = hbw />

The snake pipefish is occasionally eaten, but it has poor nutritional value. The amount of these fish is increasing in the common murre's diet. Since 2003, the snake pipefish has increased in numbers in the North-east Atlantic and North Sea and sandeel numbers have declined.<ref name = harris2008>Harris et al. (2008)</ref>

BreedingEdit

ColoniesEdit

File:Murre colony.jpg
Part of a U. a. californica colony, Farallon Islands, California

The common murre nests in densely packed colonies (known as "loomeries"Template:Citation needed), with up to twenty pairs occupying one square metre at peak season.Template:Citation needed Common murres do not make nests and lay their eggs on bare rock ledges, under rocks, or the ground. Despite the high density of murre breeding sites, sites may vary greatly in their quality over small spatial scales. Pairs breeding at those sites of highest quality are more likely to be occupied by a breeding pairs at all population sizes, and more likely to successfully fledge a chick.<ref name="Bennett2022">Template:Cite journal</ref> They first breed at four to nine years old,<ref name=":0">Template:Cite journal</ref> but most individuals recruit into the breeding population at ages six or seven,<ref name=":0" /> although birds may disperse (permanently depart their natal colony) if space is limited. Annual survival probability for birds aged 6–15 is 0.895,<ref name=":0" /> and average lifespan is about 20 years. Breeding success increases with age up to age 9–10 to 0.7 fledglings per pair, then declines in the oldest age birds, perhaps indicating reproductive senescence.<ref name=":0" />

High densities mean that birds are close contact with neighbouring breeders.<ref name = birkhead1978>Birkhead (1978)</ref> Common murres perform appeasement displays more often at high densities and more often than razorbills.<ref name = birkhead1978/> Allopreening is common both between mates and between neighbours. Allopreening helps to reduce parasites, and it may also have important social functions.<ref name = lewis2007>Lewis et al. (2007)</ref> Frequency of allopreening a neighbour correlates well with current breeding success.<ref name = lewis2007/> Allopreening may function as a stress-reducer; ledges with low levels of allopreening show increased levels of fighting and reduced breeding success.<ref name =lewis2007/>

CourtshipEdit

Courtship displays including bowing, billing and mutual preening. The male points its head vertically and makes croaking and growling noises to attract the females. The species is monogamous, but pairs may split if breeding is unsuccessful.<ref name = kokko2004>Kokko et al. (2004)</ref><ref name = moody2005>Moody et al. (2005)</ref>

Eggs and incubationEdit

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File:Uria aalge MHNT Box Rouzic.jpg
Murre eggs

Common murre eggs are large (around 11% of female weight<ref name = gaston1998>Gaston & Jones (1998)</ref>), and are pointed at one end. The egg's pyriform shape is popularly ascribed the function of allowing the egg to spin on its axis or in an arc when disturbed, however there is no evidence to support this claim.<ref name="pyriformegg">Template:Cite journal</ref> Various hypotheses have arisen to explain the egg's shape:

  1. Pyriform eggs are more stable on a sloping surface than more elliptical eggs, such as that of the razorbill.<ref name="pyriformegg" />
  2. The shape allows efficient heat transfer during incubation.<ref name=johnson1941>Johnson (1941)</ref>
  3. As a compromise between large egg size and small cross-section. Large size allows quick development of the chick. Small cross-sectional area allows the adult bird to have a small cross-section and therefore reduce drag when swimming.<ref name=gaston1998/>
  4. Due to its pyriform shape, a higher proportion of the eggshell is in contact with the cliff minimising the effects of impact by neighbouring birds.
  5. It helps to confine faecal contamination to the pointy end of the egg. The blunt end, where the embryo's head and air cell are located, is kept relatively free of debris, allowing gases to pass through the shell unimpeded;.<ref>Template:Cite journal</ref><ref name="pyriformegg" />

Eggs are laid between May and July for the Atlantic populations and March to July for those in the Pacific. The female spends less time ashore during the two weeks before laying. When laying, she assumes a "phoenix-like" posture: her body raised upright on vertical tarsi; wings half outstretched. The egg emerges point first and laying usually takes 5–10 minutes.<ref name=harris2006>Harris & Wanless (2006)</ref>

File:Common guillemot egg theft.ogv
Herring gull steals an egg, Lundy

The eggs vary in colour and pattern to help the parents recognize them, each egg's pattern being unique.<ref>Template:Cite book</ref> Colours include white, green, blue or brown with spots or speckles in black or lilac. After laying, the female will look at the egg before starting the first incubation shift.<ref name=harris2006/> Both parents incubate the egg using a single, centrally located brood patch for the 28 to 34 days to hatching in shifts of 1–38 hours.<ref name=gaston1998/>

Eggs can be lost due to predation or carelessness. Crows and gulls are opportunist egg thieves. Eggs are also knocked from ledges during fights. If the first egg is lost, the female may lay a second egg. This egg is usually lighter than the first, with a lighter yolk.Template:Citation needed Chicks from second eggs grow quicker than those from first eggs. However this rapid growth comes at a cost, first chicks have larger fat reserves and can withstand temporary shortages of food.Template:Citation needed

Growth of the chickEdit

Chicks occupy an intermediate position between the precocial chicks of genus Synthliboramphus and the semi-precocial chicks of the Atlantic puffin.<ref name = gaston1985>Gaston (1985)</ref> They are born downy and by 10 days old they are able to regulate their own temperature.<ref name = mahoney1981>Mahoney & Threlfall(1981)</ref> Except in times of food shortage there is at least one parent present at all times, and both parents are present 10–30% of the time.<ref name = wanless2005 >Wanless et al. (2005)</ref> Both parents alternate between brooding the chick or foraging for food.

File:Guillemot theora conversion test.ogv
Adults feeding chick, Lundy

Provisioning is usually divided equally between each parent, but unequal provisioning effort can lead to divorce.<ref name = moody2005/> Common murres are single-prey loaders, this means that they carry one fish at time. The fish is held lengthways in the adult's bill, with the fish's tail hanging from the end of the beak. The returning adult will form its wings into a 'tent' to protect the chick. The adult points its head downwards and the chick swallows the fish head first.

Alloparenting behaviour is frequently observed. Non-breeding and failed breeders show great interest in other chicks, and will attempt to brood or feed them. This activity is more common as the chicks get older and begin to explore their ledge. There has also been a record of a pair managing to raise two chicks.<ref name = harris2000 >Harris et al. (2000)</ref> Adults that have lost chicks or eggs will sometimes bring fish to the nest site and try to feed their imaginary chick.

At time of extreme food stress, the social activity of the breeding ledge can break down. On the Isle of May colony in 2007, food availability was low. Adults spent more of their time-budget foraging for their chicks and had to leave them unattended at times. Unattended chicks were attacked by breeding neighbour which often led to their deaths. Non-breeding and failed breeders continued to show alloparental care.<ref name = ashbrook2008 >Ashbrook et al. (2008)</ref>

File:Murre Chick by Ryan deRegnier USFWS.jpg
Chick, Alaska

The chicks will leave the nest after 16 to 30 days (average 20–22 days),<ref name = harris1985/> and glide down into the sea, slowing their fall by fluttering as they are not yet able to fly. Chicks glide from heights as high as Template:Convert to the water below.Template:Citation needed Once the young chick has left the nest, the male is in close attendance for up to two months. The chicks are able to fly roughly two weeks after fledging. Up until then the male feeds and cares for the chick at sea. In its migration south the chick swims about Template:Convert. The female remains at the nest site for up to 36 days after the chick has fledged (average 16 days).<ref name = harris2003>Harris & Wanless (2003)</ref>

Relationship with humansEdit

Template:Multiple image

PollutionEdit

Major oil spills double the winter mortality of breeding adults but appear to have little effect on birds less than three years old.<ref name = votier2008>Votier et al. (2008)</ref> This loss of breeding birds can be compensated by increased recruitment of 4–6 year olds to breeding colonies.<ref name = votier2008/>

Recreational disturbanceEdit

Nesting common murres are prone to two main sources of recreational disturbance: rock-climbing and birdwatching. Sea cliffs are a paradise for climbers as well as birds; a small island like Lundy has over 1000 described climbing routes.<ref name = harrison2008>Harrison (2008)</ref> To minimise disturbance, some cliffs are subject to seasonal climbing bans.<ref name= harrison2008/>

Birdwatching has conflicting effects on common murres. Birdwatchers petitioned the UK government to introduce the Sea Birds Preservation Act 1869. This act was designed to reduce the effects of shooting and egg collecting during the breeding season.<ref name=barclaysmith1959>Barclay-Smith (1959)</ref> Current concerns include managing the effect of visitor numbers at wildlife reserves. Common murres have been shown to be sensitive to visitor numbers.<ref name = beale2007>Beale (2007)</ref>

Seabirds as indicators of marine healthEdit

When common murres are feeding their young, they return with one fish at a time. The provisioning time relates to the distance of the feeding areas from the colony and the numbers of available fish. There is a strong non-linear relationship between fish density and colony attendance during chick-rearing.<ref name = harding2007>Harding et al. (2007)</ref>

As a food sourceEdit

In areas such as Newfoundland and Labrador, the birds, along with the related thick-billed murre, are referred to as 'turrs' or 'tuirs', and are consumed. The meat is dark and quite oily, due to the birds' diet of fish. Eggs have also been harvested. Eggers from San Francisco took almost half a million eggs a year from the Farallon Islands in the mid-19th century to feed the growing city.<ref>White, Peter; (1995)</ref>

Mass mortality in global warmingEdit

A 2024 study<ref>Template:Cite journal</ref> in the journal Science has reported that an extreme marine heatwave has killed approximately half of Alaska's Common murre. Between the 7-year period before (2008–2014) and after (2016–2022) the heatwave, murre numbers plummeted 52 to 78% at 13 colonies, lost 4.00 million common murres, which is the largest documented wildlife mortality event in the modern era. No evidence of recovery has yet been observed.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

NotesEdit

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ReferencesEdit

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External linksEdit

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