Razorbill | |
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On Skomer Island, Pembrokeshire, Wales | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Charadriiformes |
Family: | Alcidae |
Genus: | Alca |
Species: | A. torda |
Binomial name | |
Alca torda | |
Subspecies [3] | |
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The razorbill, razor-billed auk, [4] or lesser auk [5] (Alca torda) is a North Atlantic colonial seabird and the only extant member of the genus Alca of the family Alcidae, the auks. It is the closest living relative of the extinct great auk (Pinguinus impennis). [6]
Razorbills are primarily black with a white underside. The male and female are identical in plumage; however, males are generally larger than females. This agile bird, which is capable of both flight and diving, has a predominantly aquatic lifestyle and only comes to land in order to breed. It is monogamous, choosing one partner for life. Females lay one egg per year. Razorbills nest along coastal cliffs in enclosed or slightly exposed crevices. The parents spend equal amounts of time incubating, and once the chick has hatched, they take turns foraging for their young.
In 1918, the razorbill was protected in the United States by the Migratory Bird Treaty Act. Presently, this species faces major threats, including the destruction of breeding sites, [7] oil spills, [8] and deterioration of food quality. The IUCN records the population of the species as fluctuating, [1] causing its status to interchange. It has been recorded that the population had increased from 2008 to 2015, [9] decreased from 2015 to 2021, [10] and appears to be increasing or stable at the present. [1] It is estimated that the current global razorbill population lies between 838,000 to 1,600,000 individuals. [1]
The genus Alca was introduced in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae . [11] The genus name Alca is from Norwegian Alke, and torda is from törd a Gotland Swedish dialect word. Both terms refer to this species. [12] The word Alca had been used by earlier authors for the razorbill such as Carolus Clusius in 1605 [13] and Francis Willughby in 1676. [14]
The razorbill (Alca torda) is now the sole species in the genus Alca. [15] Its close relative, the great auk (Pinguinus impennis), became extinct in the mid-19th century. Razorbills and great auks are part of the tribe Alcini, which also includes the common murre or common guillemot (Uria aalge), the thick-billed murre (Uria lomvia), and the dovekie (Alle alle). [16]
There are two subspecies of razorbill recognized by the American Ornithologists' Union.
Image | Subspecies | Distribution |
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Alca torda torda Linnaeus 1758 | the Baltic and White Seas, Norway, Bear Island, Iceland, Greenland, and eastern North America. | |
Alca torda islandica C.L. Brehm 1831 | Ireland, Great Britain, and northwestern France. | |
The two subspecies differ slightly in bill measurements.
A third subspecies, Alca torda pica, is no longer recognized because the distinguishing characteristic, an additional furrow in the upper mandible, is now known to be age-related.
The razorbill has a white belly and a black head, neck, back, and feet during the breeding season. A thin white line also extends from the eyes to the end of the bill. Its head is darker than that of a common murre. During the non-breeding season, the throat and face behind the eye become white, and the white line on the face and bill becomes less prominent. [17] The bill is black, deep and laterally compressed, with a blunt end. It has several vertical grooves or furrows near the curved tip, one of them adorned with a white, broken vertical line. The bill is thinner and the grooves are less marked during the non-breeding season. It is a large and thick-set bird, for an alcid, and its mean weight ranges from 505 to 890 g (17+3⁄4 to 31+1⁄2 oz). [18] The female and male adults are very much alike, having only small differences such as wing length. It is 37–39 cm in body length, the wing length of adult males ranges from 201–216 mm (7+15⁄16–8+1⁄2 in) while that of females ranges from 201 to 213 mm (7+15⁄16 to 8+3⁄8 in). [19] During incubation, this species has a horizontal stance and the tail feathers are slightly longer in the center in comparison to other alcids. This makes the razorbill have a distinctly long tail which is not common for an auk. In-flight, the feet do not protrude beyond the tail.
Their mating system is female-enforced monogamy; the razorbill pairs for life. It nests in open or hidden crevices among cliffs and boulders. It is a colonial breeder and only comes to land to breed. The annual survival rate of the razorbill is between 89 and 95%. [20] Though the razorbill's average lifespan is roughly 13 years, a bird ringed in the UK in 1967 survived for at least 41 years—a record for the species. [21]
Razorbills are distributed across the North Atlantic; the world population of razorbills is estimated to be at less than 1,000,000 breeding pairs (Chapdelaine et al. 2001). Approximately half of the breeding pairs occur in Iceland. Razorbills thrive at water surface temperatures below 15 °C. They are often seen with the two larger auks, thick-billed murre and common murre. However, unlike other auks, they commonly move into larger estuaries with lower salinity levels to feed. These birds are distributed across sub-arctic and boreal waters of the Atlantic. Their breeding habitat is islands, rocky shores, and cliffs on northern Atlantic coasts, in eastern North America as far south as Maine, and in western Europe from northwestern Russia to northern France. North American birds migrate offshore and south, ranging from the Labrador Sea south to the Grand Banks of Newfoundland to New England. Eurasian birds also winter at sea, with multiple populations aggregating in the North Sea [22] and some moving south as far as the western Mediterranean. Approximately 60 to 70% of the entire razorbill population breeds in Iceland. [23]
Some razorbill colonies include (north to south):
The life-history traits of the razorbill are similar to that of the common murre. However, razorbills are slightly more agile. It is a fully migratory and a naval bird, as during the colder months, it leaves land and spends the entire winter in the waters of the Atlantic Ocean. [26]
During breeding, both males and females protect the nest. Females select their mate and will often encourage competition between males before choosing a partner. [27] Once a male is chosen, the pair will stay together for life.
Individuals only breed at 3–5 years of age. As pairs grow older they will occasionally skip a year of breeding. A mating pair will court several times during breeding periods to strengthen their bond. [18] Courtship displays include touching bills and following one another in elaborate flight patterns. Once the pre-laying period begins, males will constantly guard their mates by knocking other males away with their bills. [18] The pair will mate up to 80 times in a 30-day period to ensure fertilization. [28] Females will sometimes encourage other males to engage in copulation to guarantee successful fecundity. [27]
Throughout the pre-laying period, razorbills will socialize in large numbers. Two types of socializing occur: large groups dive and swim together in circles repeatedly and all rise up to the surface, heads first and bills open; secondly, large groups swim in a line weaving across each other in the same direction.
Nest site choice is very important for these birds to ensure the protection of the young from predators. Unlike murres, nest sites are not immediately alongside the sea on open cliff ledges but at least 10 cm (4 in) away, in crevices on cliffs or among boulders. Nests are usually confined among the rocks or slightly more open. Some sites are along ledges, however, crevice sites seem to be more successful due to reduced predation. [29]
The mating pair will often reuse the same site every year. [30] [31] Since chicks cannot fly, nests close to the sea provide easy access when leaving the colony. Generally, razorbills do not build a nest; however, some pairs often use their bills to drag material upon which to lay their egg. [32] Nest under a boulder, rarely on an exposed ledge, may use Puffin or rabbit burrow. [33] Although gregarious in breeding colonies, nests are not contiguous, but some meters apart, resulting in less aggression than in Guillemot colonies. [33]
Females lay a single egg per year, usually from late April to May. The egg is an ovoid-pyramidal shape, cream color with has dark brown blotches. Incubation starts generally 48 hours after laying the egg. Females and males take turns incubating the egg several times daily for a total of approximately 35 days before hatching occurs. Razorbill chicks are semi-precocial. [34] During the first two days after hatching, the chick will spend the majority of its time under the parent's wing. There is always one parent at the nest site while the other goes to sea to collect food for the chick. The hatchling develops a complete sheath 10 days after hatching. After 17–23 days, the chick leaves the nest by jumping from a cliff, closely followed by the male parent, who will accompany the chick to sea. During this time, the male parent will dive more than the female parent. [35]
Razorbills dive deep into the sea using their semi-folded wings and their streamlined bodies to propel themselves toward their prey. They keep their feet spread. While diving, they rarely stay in groups but rather spread out to feed. The majority of their feeding occurs at a depth of 25 m (80 ft) but they have the ability to dive up to 120 m (395 ft) below the surface. [36] During a single dive, an individual can capture and swallow many schooling fish, depending on their size. Razorbills spend approximately 44% of their time foraging at sea. [37]
When feeding their young, they generally deliver small loads. Adults will mainly feed only one fish to their chick with high feeding deliveries at dawn and decreased feeding 4 hours before dark. [18] Females will generally feed their chicks more frequently than males. [37] They may well fly more than 100 km (60 mi) out to sea to feed when during egg incubation, but when provisioning the young, they forage closer to the nesting grounds, some 12 km (7+1⁄2 mi) away, and often in shallower water. [24]
The diet of razorbill is very similar to that of a common murre or common guillemot. It consists generally of mid-water schooling fish such as capelin, sand lance, juvenile cod, sprats, and herring. It may also include crustaceans and polychaetes. A recent study suggests the razorbill's diet is affected by local and regional environmental conditions in the marine environment [31]
The adult razorbill has several predators which include: polar bears, great black-backed gulls, peregrine falcons, ravens, crows, and jackdaws. The general predators of their eggs are gulls and ravens. The best chance for adult razorbill to avoid predation is by diving. Arctic foxes can also predate significant numbers of adults, eggs, and chicks in some years. [38]
Razorbill eggs were collected until the late 1920s in Scotland's remote St Kilda islands by their men scaling the cliffs. The eggs were buried in St Kilda peat ash to be eaten through the cold, northern winters. The eggs were considered to taste like duck eggs in taste and nourishment. [39]
In the early 20th century, razorbills were harvested for eggs, meat, and feathers. This greatly decreased the global population. In 1917, they were finally protected by the “Migratory Bird Treaty Act” which reduced hunting. [18] Other threatening interactions include oil pollution which can damage breeding sites. Any damage to breeding sites can reduce possible nest sites and affect the reproduction of the species. Commercial fishing affects populations because razorbills can become tangled in nets. Overfishing also decreases the abundance of razorbill prey and thus affects their survival.
While the razorbill is the only living species, the genus Alca had a much higher diversity in the Pliocene. Some ornithologists also feel it is appropriate to retain the great auk in the genus Alca, instead of Pinguinus. [40] A number of fossil forms have been found:
As far as is known, the genus Alca seems to have evolved in the western North Atlantic or the present-day Caribbean like most other Alcini. Its ancestors would have reached these waters through the still-open Isthmus of Panama during the Miocene. [41]
The great auk is a species of flightless alcid that became extinct in the mid-19th century. It was the only modern species in the genus Pinguinus. It is not closely related to the Southern Hemisphere birds now known as penguins, which were discovered later by Europeans and so named by sailors because of their physical resemblance to the great auk, which were called penguins.
The tufted puffin, also known as crested puffin, is a relatively abundant medium-sized pelagic seabird in the auk family (Alcidae) found throughout the North Pacific Ocean. It is one of three species of puffin that make up the genus Fratercula and is easily recognizable by its thick red bill and yellow tufts.
Puffins are any of three species of small alcids (auks) in the bird genus Fratercula. These are pelagic seabirds that feed primarily by diving in the water. They breed in large colonies on coastal cliffs or offshore islands, nesting in crevices among rocks or in burrows in the soil. Two species, the tufted puffin and horned puffin, are found in the North Pacific Ocean, while the Atlantic puffin is found in the North Atlantic Ocean.
An auk or alcid is a bird of the family Alcidae in the order Charadriiformes. The alcid family includes the murres, guillemots, auklets, puffins, and murrelets. The family contains 25 extant or recently extinct species that are divided into 11 genera.
The black-throated loon, also known as the Arctic loon and the black-throated diver, is a migratory aquatic bird found in the northern hemisphere, primarily breeding in freshwater lakes in northern Europe and Asia. It winters along sheltered, ice-free coasts of the north-east Atlantic Ocean and the eastern and western Pacific Ocean. This loon was first described by Carl Linnaeus in 1758 and has two subspecies. It was previously considered to be the same species as the Pacific loon, of which it is traditionally considered to be a sister species, although this is debated. In a study that used mitochondrial and nuclear intron DNA, the black-throated loon was found to be sister to a clade consisting of the Pacific loon and two sister species, the common loon and the yellow-billed loon.
Guillemot is the common name for several species of seabird in the Alcidae or auk family. In Europe, the term covers two genera: Uria and Cepphus. In North America the Uria species are called murres and only the Cepphus species are called "guillemots". This word of French origin derives from a form of the name William, cf. French: Guillaume.
The black guillemot or tystie is a medium-sized seabird of the Alcidae family, native throughout northern Atlantic coasts and eastern North American coasts. It is resident in much of its range, but large populations from the high arctic migrate southwards in winter. The bird can be seen in and around its breeding habitat of rocky shores, cliffs and islands in single or smalls groups of pairs. They feed mainly by diving towards the sea floor feeding on fish, crustaceans or other benthic invertebrates. They are listed on the IUCN red list as a species of least concern.
The pigeon guillemot is a species of bird in the auk family, Alcidae. One of three species in the genus Cepphus, it is most closely related to the spectacled guillemot. There are five subspecies of the pigeon guillemot; all subspecies, when in breeding plumage, are dark brown with a black iridescent sheen and a distinctive wing patch broken by a brown-black wedge. Its non-breeding plumage has mottled grey and black upperparts and white underparts. The long bill is black, as are the claws. The legs, feet, and inside of the mouth are red. It closely resembles the black guillemot, which is slightly smaller and lacks the dark wing wedge present in the pigeon guillemot.
The common murre, also called the common guillemot or foolish guillemot, 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.
The little auk or dovekie is a small auk, the only member of the genus Alle. Alle is the Sami name of the long-tailed duck; it is onomatopoeic and imitates the call of the drake duck. Linnaeus was not particularly familiar with the winter plumages of either the auk or the duck, and appears to have confused the two species. Other common names include rotch, rotche,, bullbird, and sea dove, although the latter sometimes refers to a relative of dovekies, the black guillemot.
The thick-billed murre or Brünnich's guillemot is a bird in the auk family (Alcidae). This bird is named after the Danish zoologist Morten Thrane Brünnich. The very deeply black North Pacific subspecies Uria lomvia arra is also called Pallas' murre after its describer. The genus name is from Ancient Greek ouria, a waterbird mentioned by Athenaeus. The species term lomvia is a Swedish word for an auk or diver. 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.
The horned puffin is an auk found in the North Pacific Ocean, including the coasts of Alaska, Siberia and British Columbia. It is a pelagic seabird that feeds primarily by diving for fish. It nests in colonies, often with other auks.
The parakeet auklet is a small seabird of the North Pacific. Parakeet Auklets used to be placed on its own in the genus Cyclorrhynchus but recent morphological and genetic evidence suggest it should be placed in the genus Aethia, making them closely related to crested auklets and least auklets. It is associated with the boreal waters of Alaska, Kamchatka and Siberia. It breeds on the cliffs, slopes and boulder fields of offshore islands, generally moving south during the winter.
The rhinoceros auklet is a seabird and a close relative of the puffins. It is the only extant species of the genus Cerorhinca. Given its close relationship with the puffins, the common name rhinoceros puffin has been proposed for the species.
Aechmophorus is a genus of birds in the grebe family.
The crested auklet is a small seabird of the family Alcidae, distributed throughout the northern Pacific and the Bering Sea. The species feeds by diving in deep waters, eating krill and a variety of small marine animals. It nests in dense colonies of up to 1 million individuals in the Bering Sea and the Sea of Okhotsk. It often breeds in mixed-species colonies with the least auklet, a smaller congener.
Pinguinus alfrednewtoni is an extinct species of auk related to the great auk known from fossils that were discovered in the Pliocene Yorktown Formation of North Carolina. Like the great auk, it was a large flightless diving bird that used its wings to propel itself forward underwater. Only a limited amount of material is known, despite the rich diversity of fossil auks recovered from the Yorktown Formation. Due to this, it has been proposed that it was either a more coastal animal or simply not as common in more southern waters. This later suggestion could be supported by the discovery of relatively young P. alfrednewtoni remains, indicating that they may have overwintered in the region. One early hypothesis proposed that it was a direct ancestor to the great auk, but this idea is no longer supported. Instead, it is thought that it filled the same niche as its eastern relative, which eventually expanded into the western Atlantic after the extinction of P. alfrednewtoni.
The term seabird is used for many families of birds in several orders that spend the majority of their lives at sea. Seabirds make up some, if not all, of the families in the following orders: Procellariiformes, Sphenisciformes, Pelecaniformes, and Charadriiformes. Many seabirds remain at sea for several consecutive years at a time, without ever seeing land. Breeding is the central purpose for seabirds to visit land. The breeding period is usually extremely protracted in many seabirds and may last over a year in some of the larger albatrosses; this is in stark contrast with passerine birds. Seabirds nest in single or mixed-species colonies of varying densities, mainly on offshore islands devoid of terrestrial predators. However, seabirds exhibit many unusual breeding behaviors during all stages of the reproductive cycle that are not extensively reported outside of the primary scientific literature.
Bird cliffs, or nesting cliffs, are steep cliffs with numerous small shelves which serve as nesting locations for bird colonies. Bird cliffs are found on islands in the North Atlantic and Arctic, such as the Faroe Islands, Iceland, the Svalbard archipelago and on islands off Northern Norway. Among species that nest in large numbers on bird cliffs are common murre, thick-billed murre, razorbill, kittiwake, little auk and Atlantic puffin. The number of breeding couples may exhibit large variations depending on available food. Bird cliffs have often been exploited as a food resource by the local population, as well as being used by hunters and egg collectors.
The cognitive ecology of individual recognition has been studied in many species, especially in primates or other mammalian species that exhibit complex social behaviours, but comparatively little research has been done on colonial birds. Colonial birds live in dense colonies in which many individuals interact with each other daily. For colonial birds, being able to identify and recognize individuals can be a crucial skill.