Common Murre

识别特征

The common murre is 38–46 cm (15–18 in) in length with a 61–73 cm (24–29 in) wingspan. Male and female are indistinguishable in the field and weight ranges between .mw-parser-output .frac{white-space:nowrap}.mw-parser-output .frac .num,.mw-parser-output .frac .den{font-size:80%;line-height:0;vertical-align:super}.mw-parser-output .frac .den{vertical-align:sub}.mw-parser-output .sr-only{border:0;clip:rect(0,0,0,0);clip-path:polygon(0px 0px,0px 0px,0px 0px);height:1px;margin:-1px;overflow:hidden;padding:0;position:absolute;width:1px}945 g (2 lb 1+1⁄2 oz) in the south of their range to 1,044 g (2 lb 5 oz) in the north. A weight range of 775–1,250 g (1 lb 11+1⁄2 oz – 2 lb 12 oz) has been reported. In breeding plumage, the nominate subspecies (U. a. aalge) is black on the head, back and wings, and has white underparts. It has thin dark pointed bill and a small rounded dark tail. After the pre-basic moult, the face is white with a dark spur behind the eye. Birds of the subspecies U. a. albionis are dark brown rather than black, most obviously so in colonies in southern Britain. Legs are grey and the bill is dark grey. Occasionally, adults are seen with yellow/grey legs. In May 2008, an aberrant adult was photographed with a bright yellow bill.<p>The plumage of first winter birds is the same as the adult basic plumage. However, the first pre-alternate moult occurs later in the year. The adult pre-alternate moult is December–February, (even starting as early as November in U. a. albionis). First year birds can be in basic plumage as late as May, and their alternate plumage can retain some white feathers around the throat.<p>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—perhaps character displacement with the northerly thick-billed murre, which has a white bill-stripe but no bridled morph. The white is highly contrasting especially in the latter species and would provide an easy means for an individual bird to recognize conspecifics in densely packed breeding colonies.<p>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.<p>The common murre flies with fast wing beats and has a flight speed of 80 km/h (50 mph). Groups of birds are often seen flying together in a line just above the sea surface. However, a high wing loading of 2 g/cm2 means that this species is not very agile and take-off is difficult. Common murres become flightless for 45–60 days while moulting their primary feathers. The sound of the wing beats of the murres are often described as similar to a helicopter.<p>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 30 m (100 ft) on a regular basis. Diving depths up to 180 m (590 ft) have been recorded and birds can remain underwater for a couple of minutes.

分类信息

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.<p>The binomial name derives from Greek ouriaa, a waterbird mentioned by Athenaeus, and Danish aalge, "auk" (from Old Norse alka).<p>The English "guillemot" is from French guillemot, probably derived from Guillaume, "William". "Murre" is of uncertain origins, but may imitate the call of the common guillemot.<p>The official common name for this species is Common Murre according to the IOC World Bird List, Version 11.2. Unofficial names include common guillemot, used in the UK.

学名

Uria aalge

命名信息

(Pontoppidan, 1763)

目

Charadriiformes

科

Alcidae

属

Uria

分布与栖息地

The breeding habitat is islands, rocky shores, cliffs and sea stacks. The population is large, perhaps 7.3 million breeding pairs or 18 million individuals. 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. 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.<p>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. 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.

繁殖区

NA, PAL : subarctic to temperate (locally Arctic) n coasts

非繁殖区

to Virginia in Gulf Stream (w North Atlantic); to Iberian Pen. (e North Atlantic); to n Japan (w North Pacific); to nw Baja California (nw Mexico; e North Pacific)

迁徙

Complete migrants

行为

Migration pattern: Complete migrants.

保护状况

Population trend: rising.

种群趋势

rising