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Razorbill
On Stora Karlsö, Gotland, Sweden
Pair of Razorbills calling, recorded on Skokholm, Wales
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Charadriiformes
Family: Alcidae
Genus: Alca
Species:
A. torda
Binomial name
Alca torda
Subspecies[3]
  • A. t. torda - Linnaeus, 1758
  • A. t. islandica - Brehm, CL, 1831

The razorbill (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).[4] Historically, it has also been known as "auk",[5] "razor-billed auk"[6] and "lesser auk".[7]

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.

Presently, this species faces major threats, including the destruction of breeding sites,[8] oil spills,[9] 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,[10] decreased from 2015 to 2021,[11] and appears to be increasing or stable at the present.[1] It is estimated that the current global razorbill population lies between 838,000 and 1,600,000 individuals.[1] In 1918, the razorbill was protected in the United States by the Migratory Bird Treaty Act.

Taxonomy

[edit]
In flight off Skomer Island

The genus Alca was formally described in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae.[12] The genus name Alca is from Norwegian Alke, and torda is from törd a Gotland Swedish dialect word; both terms refer to this species.[13] The type locality is Stora Karlsö, just off the west coast of Gotland, Sweden.[14] The word Alca had been used for the razorbill by earlier authors such as Carolus Clusius in 1605[15] and Francis Willughby in 1676.[16]

The razorbill (Alca torda) is now the sole species in the genus Alca,[17] though its close relative, the great auk (Pinguinus impennis), which became extinct in the mid-19th century, was also formerly included in the genus Alca.[12] 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 or Brünnich's guillemot (Uria lomvia), and the little auk (Alle alle).[18]

There are two subspecies of razorbill accepted by the IOC:[17]

Image Subspecies Distribution

Stora Karlsö, Gotland, Sweden		 Alca torda torda Linnaeus 1758 the Baltic and White Seas, Norway, Bear Island, Greenland, and eastern North America.

Látrabjarg, Iceland (with Atlantic puffins to the right)		 Alca torda islandica C.L. Brehm 1831 Iceland (type locality), Ireland, Great Britain, northwestern France, and Heligoland, Germany.

The two subspecies differ slightly in size and bill measurements, with A. t. islandica, which occurs in warmer waters, being slightly smaller.[14] A third subspecies Alca torda pica Linnaeus, 1766 (originally described as a species Alca pica from the Arctic,[19] and reduced to subspecies by Salomonsen in 1944[20]), is no longer accepted because the distinguishing characteristic, an additional furrow in the upper mandible, is now known to be age-related.[14]

Description

[edit]

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.[21] 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).[22] 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).[23] 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%.[24] 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.[25]

Distribution and habitat

[edit]

Razorbills are distributed across the North Atlantic; the world population of razorbills is estimated to be at less than 1,000,000 breeding pairs.[26] Approximately half of the breeding pairs occur in Iceland. Razorbills thrive at water surface temperatures below 15 °C (59 °F). 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[27] and some moving south as far as the western Mediterranean. Approximately 60 to 70% of the entire razorbill population breeds in Iceland.[28]

Some razorbill colonies include (north to south):

Behaviour

[edit]
Taking off from water

The life-history traits of the razorbill are similar to that of the common murre. However, razorbills are slightly more agile. In North America it is a largely migratory seabird, as during the colder months, it leaves land and spends the entire winter in the waters of the Atlantic Ocean,[34] though western European birds often remain close to their breeding sites.

During breeding, both males and females protect the nest. Females select their mate and will often encourage competition between males before choosing a partner.[35] Once a male is chosen, the pair will stay together for life.

Reproduction

[edit]
Courting on Skomer Island

Individuals only breed at 3–5 years old. 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.[22] 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.[22] The pair will mate up to 80 times in a 30-day period to ensure fertilisation.[36] Females will sometimes encourage other males to engage in copulation to guarantee successful fecundity.[35]

Throughout the pre-laying period, razorbills will gather in large numbers. Two types of social behaviour 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 sites

[edit]
Banded chick on Gannet Island, Labrador

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.[37]

The mating pair will often reuse the same site every year.[38][39] 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 may use their bills to drag material upon which to lay their egg.[40] Nest under a boulder, rarely on an exposed ledge, may use Puffin or rabbit burrow.[41] Although gregarious in breeding colonies, nests are not contiguous, but some metres apart, resulting in less aggression than in Guillemot colonies.[41]

Incubation and hatching

[edit]
Egg

Females lay a single egg per year, usually from late April to May. The egg is an ovoid-pyramidal shape, creamy white to pale brown 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.[42] 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.[43]

Feeding

[edit]

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.[44] 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.[45]

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.[22] Females will generally feed their chicks more frequently than males.[45] They may 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.[29]

Diet

[edit]

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, sandeels, juvenile cod, sprats, and herring. It may also include crustaceans and polychaetes. A recent study suggests the diet is affected by local and regional environmental conditions in the marine environment.[39]

Predators

[edit]

The adult razorbill has several predators which include 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 and polar bears can also predate significant numbers of adults, eggs, and chicks in some years in the north of the species' range.[46]

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.[47]

Conservation and management

[edit]
Razorbills on Machias Seal Island Migratory Bird Sanctuary

In the early 20th century, razorbills were harvested for eggs, meat, and feathers. This greatly decreased the global population. In the USA, they were finally protected by the 1917 Migratory Bird Treaty Act which reduced hunting.[22] 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.

Evolution and prehistoric species

[edit]

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.[48] A number of fossil forms have been found:

  • Alca "antiqua" (Late Miocene/Early Pliocene of Lee Creek Mine, US)[citation needed]
  • Alca sp. (Late Miocene/Early Pliocene of Lee Creek Mine, US) - possibly A. stewarti
  • Alca stewarti (Kattendijk Sands Early Pliocene of Belgium)
  • Alca ausonia (Yorktown Early Pliocene of Lee Creek Mine, US - Middle Pliocene of Italy)
  • Alca sp. (Puerto de Mazarrón Pliocene of El Alamillo, Spain) - may be A. antiqua or A. ausonia

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.[49]

References

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Razorbill

View on Grokipedia
from Grokipedia
The Razorbill (Alca torda) is a medium-sized colonial belonging to the auk family Alcidae, native to the North , distinguished by its distinctive black-and-white plumage, heavy and sharply pointed bill, and expert diving abilities. It measures approximately 37–39 cm in length with a of 60–69 cm, featuring a glossy black upper body and head during the breeding season, white underparts, and a thick deep black bill marked with white vertical lines extending toward the eyes and a bright yellow visible inside the mouth. Razorbills inhabit coastal cliffs and offshore islands across the North Atlantic, breeding from the and eastern northward to , , and , while wintering in offshore waters as far south as the Mediterranean and southern . They are highly adapted to , spending much of their time at where they forage by diving to depths of up to 100 meters (typically 20–30 meters) using their wings for propulsion underwater to catch small schooling fish such as , sand lance, and , with adults delivering 1–6 fish per meal to their young. On land, they exhibit agile but somewhat clumsy waddling due to their short legs, and in flight, they beat their wings rapidly while keeping their necks extended, often flying low over the water in lines. Breeding occurs in dense colonies from May to June, where pairs—typically monogamous and returning to the same site annually—nest in rock crevices or on ledges, laying a single large, pear-shaped that both parents incubate for about 35 days until hatching. Chicks grow rapidly on a diet and flightlessly at 18–23 days old by jumping from high cliffs into the sea, after which the male parent cares for them at sea for several weeks until they can fly. Razorbills can live up to 41 years in the wild, though many succumb earlier to threats. Globally, the Razorbill population is estimated at 838,000–1,660,000 mature individuals as of , with about 90% in , primarily in (41%) and the , and the species is currently classified as Least Concern by the IUCN, with overall stable or increasing trends despite localized declines from threats including climate change impacts on , bycatch in fishing gillnets, oil , and human disturbances. Conservation efforts include bycatch reduction campaigns in regions like and monitoring programs in to protect breeding colonies from and offshore development. Populations have stabilized or increased in some areas, such as Britain and , since the 1970s.

Taxonomy and nomenclature

Etymology

The common name "Razorbill" derives from the bird's distinctive bill, which features a sharp, compressed edge likened to a razor blade. This English name reflects the prominent morphological trait of the upper , which is deep and laterally flattened for efficient capture. Historically, the bird was more commonly known simply as an "auk" before the adoption of "Razorbill," with regional variations including "razor-billed auk," "," "willock," "scout," and "marrot" in British dialects, often shared with related alcids like the . The scientific binomial Alca torda was assigned by in his (10th edition, 1758), establishing the Razorbill as the of the Alca. The name Alca originates from the term alka (also appearing in Icelandic and Swedish as álka or alke), a general designation for diving seabirds of the auk family Alcidae. The specific epithet torda is derived from the Swedish dialect word törd (or torda), meaning a black-and-white auk-like bird, with possible influences from the torda, a similar vernacular name for the species in Iberian contexts.

Classification

The razorbill (Alca torda) is the sole extant within the Alca, a monotypic in the Alcidae, which comprises the auks. It belongs to the order and the subfamily Alcinae, a group that includes other pursuit-diving seabirds such as murres () and the dovekie (Alle alle). The binomial name Alca torda was established by in 1758, reflecting its classification as a distinct auk adapted to the North Atlantic. Some authorities recognize two subspecies of the razorbill, distinguished primarily by body size and subtle bill markings, though others treat the species as monotypic. The nominate subspecies A. t. torda (described by Linnaeus in 1758) is the larger form, breeding from eastern North America through Greenland, Fennoscandia, and to northwestern Russia in the eastern Atlantic. The smaller subspecies A. t. islandica (described by Brehm in 1831) occurs in the eastern North Atlantic from Iceland and the British Isles south to northwestern France, where individuals exhibit slightly reduced dimensions and variations in bill furrows. Phylogenetically, the razorbill is the sister taxon to the extinct (Pinguinus impennis), with both forming a that is sister to the dovekie (Alle alle) within the tribe Alcini. This positioning places the razorbill closer to the dovekie and murres than to puffins (Fratercula spp.), which belong to the separate tribe Fraterculini in subfamily Aethiinae.

Physical description

Plumage and morphology

The Razorbill (Alca torda) is a medium-sized alcid with a stocky build, measuring 37–43 cm in length, with a of 60–69 cm and a weight of 505–890 g (average approximately 615 g); males are slightly larger than females. The species exhibits in size but not in , with both sexes sharing identical coloration patterns. In breeding plumage, adult Razorbills display glossy black upperparts, including the head, neck, back, and wings, contrasting with crisp underparts and underwing coverts. The bill is thick, black, and deeply grooved, crossed by a prominent white transverse line near its base, while the legs and feet are black; a thin line extends from the eye to the bill base, forming a subtle eye-ring, and the gape is bright yellow with a dark brown iris. During the non-breeding season, the plumage shifts subtly, with the throat, cheeks, and sides of the face becoming whitish, while the upperparts remain predominantly black; the white line on the bill becomes less distinct as the outer horny sheaths are partially shed. Juveniles exhibit sooty brown upperparts rather than the glossy black of adults, with a shorter, duller bill lacking the white transverse line; the underparts are white, but the overall appearance is more mottled and less contrasted. Key morphological adaptations include a deep, laterally compressed bill suited for grasping and holding multiple fish crosswise, enabling efficient underwater prey capture. The wings are short and narrow, facilitating powerful propulsion during dives rather than extended flight, with Razorbills capable of reaching depths up to 100 m. Additionally, the dense consists of waterproof feathers that trap air for and insulation, essential for the ' marine lifestyle.

Vocalizations

The Razorbill (Alca torda) primarily vocalizes during the breeding season with a low, nasal growling call that has a distinctive vibratory quality, often likened to the sound of a miniature or harsh croaking. This call serves as a territorial signal in dense breeding colonies, where it helps maintain spacing among pairs. All adult calls are variations on this growl, which is produced by both sexes without notable dimorphism in structure or pitch. Acoustically, the calls exhibit a wide range of 0.5–1.7 kHz, centered principally around 1.2 kHz, with harmonics typically at 2.4 kHz and occasionally up to 3.5–4.0 kHz. These individualized vocal signatures facilitate parent-offspring recognition amid the noisy, crowded conditions of colonies, reducing the risk of misdirected responses or confusion with neighboring pairs. Outside the breeding period, Razorbills produce minimal vocalizations and are generally silent. In , pairs engage in bill-clacking, a non-vocal but audible involving rapid snapping of the bills together, which strengthens pair bonds. When threatened, adults may emit sharper, abrupt notes as alarm signals. respond to parents with high-pitched peeping calls, particularly to solicit food deliveries at the nest site. These peeps resemble those of first-winter birds and aid in mutual recognition, though with a noted bias toward stronger paternal-chick vocal matching compared to maternal.

Distribution and habitat

Breeding range

The Razorbill (Alca torda) breeds circumpolarly across the , ranging from approximately 43°N in eastern (as far south as , ) to 73°N at in northwestern , with breeding sites confined to eastern and western (from northwestern to northwestern ). This distribution excludes the entirely, reflecting the species' adaptation to boreal and low waters with surface temperatures below 15°C. The global breeding population is estimated at 838,000–1,660,000 mature individuals (as of 2021), equivalent to roughly 419,000–830,000 breeding pairs, with Iceland hosting the largest concentration (historically 60–70% of the total, currently about 41% of the European population). Key colonies include Látrabjarg in Iceland (up to 230,000 pairs in the mid-1990s), the Gannet Islands in Newfoundland (around 10,000 pairs, the largest in North America), major sites in Scotland and the British Isles (contributing to ~145,000 pairs regionally), and colonies along the Norwegian coast such as Runde (several thousand pairs). Razorbills prefer steep coastal cliffs, rocky islands, and ledges for nesting, often under boulders or in crevices, while avoiding sandy or flat shores that offer less protection from predators. Colonies typically support up to 10,000–15,000 pairs in North American sites, with higher densities in European strongholds like . Individuals exhibit strong site fidelity, with over 90% of adults returning to the same nest site annually and approximately 83% of juveniles showing to natal colonies.

Winter range and migration

The winter range of the Razorbill (Alca torda) differs between its European and n populations, reflecting adaptations to regional oceanographic conditions. European birds, particularly those breeding in Britain and , primarily overwinter in coastal waters from the southward to the and northern , though some extend to . In , individuals disperse south from breeding areas in the and to ice-free coastal zones, with the highest concentrations occurring in the outer and ; sightings regularly reach , New York, and , becoming rarer southward to and casual to . During winter, Razorbills adopt a pelagic in open ocean environments but preferentially occupy productive coastal habitats characterized by cool waters and upwellings that support dense prey aggregations, such as those generated by tidal mixing in the . They actively avoid ice-covered areas, concentrating instead in regions like shoals and current-influenced zones that enhance efficiency. Post-breeding dispersal typically begins in to , as adults and fledglings depart colonies for southern wintering grounds, with most populations undertaking relatively short-distance migrations while southern breeders may travel longer routes. Return to breeding sites occurs between and May, often earlier in European populations (from early ) compared to North American ones (mid-April to early May). Razorbills exhibit low to specific winter sites, as evidenced by documented long-distance movements of 250 to 4,130 km between seasons, suggesting flexible use of non-breeding areas. likely relies on ocean currents to facilitate efficient travel paths, such as those in the .

Behaviour

Social structure

Razorbills exhibit a colonial , breeding in dense aggregations on coastal cliffs and offshore islands where colonies can number in the thousands of pairs, though many North American sites support fewer than 1,000 breeding pairs. Within these colonies, individuals select nest sites in rock crevices, boulder screes, or sheltered ledges, defending only a small immediately surrounding the nest, which limits inter-pair conflicts compared to with more contiguous nesting arrangements. This spacing contributes to relatively low levels of aggression during the breeding period, with interactions primarily focused on pair maintenance rather than broad hierarchical dominance. The is socially monogamous, forming strong, long-term pair bonds that often last for the lifetime of the partners, supported by high mate fidelity in returning adults. is uncommon, occurring in approximately 6% of pairs annually (as observed at the Isle of May) and typically following reproductive failure, which underscores the stability of these partnerships essential for biparental care in a challenging marine environment. Pairs reinforce their bonds through mutual allopreening, a gentle directed at the head and neck that serves both affiliative and mild agonistic functions, lasting several minutes and promoting pair cohesion without escalating to overt aggression. Outside the breeding season, Razorbills display flexible , in loose flocks typically comprising 10 to 100 individuals to exploit patchy marine resources efficiently. During winter, they aggregate into larger rafts of up to 1,000 or more birds on the water surface for resting, socializing, and communal feeding, particularly in ice-free coastal waters where such groups facilitate vigilance against predators and access to food shoals. These seasonal shifts highlight the Razorbill's adaptability in balancing solitary pair activities with gregarious strategies.

Reproduction and breeding

Razorbills breed seasonally from May to , with egg-laying typically occurring in the first week of May and continuing through early June in temperate regions, though timing shifts later at higher latitudes or in colder waters. Pairs are monogamous and often form bonds on the water during the preceding winter, engaging in displays that include bill-touching, mutual , and aerial chases to strengthen pair fidelity. Females lay a single per breeding season, though if the egg is lost early, pairs may produce a replacement in 25–57% of cases, typically within 14 days. Nesting occurs in colonies on coastal cliffs, where pairs select enclosed crevices, ledges, or burrows—often reusing sites from previous years—for from predators and ; no structured nest is built, though some sites may have minimal pebbles or vegetation. These sites are defended aggressively against intruders, including conspecifics, through vocalizations and physical confrontations. The is somewhat pyriform, aiding stability on uneven surfaces to reduce rolling risk, and both parents share incubation duties, alternating shifts multiple times daily for an average of 35 days until . Upon hatching, the semi-precocial chick emerges covered in down, capable of limited movement but requiring brooding by a parent for the first 2–3 days to maintain body temperature. Both parents then feed the chick small fish carried crosswise in the bill, provisioning every few hours for 18–25 days until the chick reaches fledging weight of about 140–180 g, at which point it remains flightless. The male parent leads the chick to sea in a direct plunge from the nest site, often from heights of tens to hundreds of meters, where the pair remains together for several weeks post-fledging. Breeding success varies with environmental conditions, averaging 0.55–0.77 fledged young per pair (70–80% in favorable years), influenced by factors like predation and availability; the limitation to one chick per season constrains recovery from poor breeding years.

Foraging and diet

Razorbills (Alca torda) are pursuit divers that primarily hunt schooling by propelling themselves using their wings in a motion, similar to flying beneath the surface. Typical dives occur at depths of 10–50 m, with mean depths around 15 m in some populations, though maximum recorded depths reach 120 m. During a single dive, they capture and swallow 5–10 small whole before surfacing. The diet of razorbills consists predominantly of fish, comprising approximately 90% of their intake by wet weight, with key prey species including sand eels (Ammodytes spp.), capelin (Mallotus villosus), herring (Clupea harengus), and sprat (Sprattus sprattus). Occasional items include crustaceans and squid, which become more prominent in winter diets, reflecting seasonal shifts in prey availability. Adults exhibit some specialization, with breeding pairs often targeting specific prey types based on local fish stocks, such as sprat-dominated diets in the Baltic Sea. To provision chicks, razorbills function as multi-prey carriers, holding 5–15 fish crosswise in their specialized bill during transport to the nest. Daily food intake for adults averages 100–200 g, often consisting of 15 or more small fish like sprat. Chicks are preferentially fed high-lipid fish species, such as capelin, to support rapid growth and development.

Predators and threats

Natural predators

The eggs and chicks of the razorbill (Alca torda) are vulnerable to predation by a variety of avian and mammalian species, particularly in colonies with accessible nest sites. Common predators include herring gulls (Larus argentatus), great black-backed gulls (Larus marinus), (Corvus corax), (Corvus corone), and corvids such as jackdaws (Corvus monedula), which opportunistically target nests during incubation and chick-rearing periods. In one study on Skokholm Island, , predation by herring gulls and jackdaws accounted for 73% of egg losses, resulting in an overall 30% loss of eggs laid. Mammalian predators such as Arctic foxes (Vulpes lagopus) in northern breeding areas and introduced (Rattus spp.) on islands further exacerbate nest vulnerability, with rats capable of causing significant chick mortality in invaded colonies. Adult razorbills face threats primarily from aerial and opportunistic predators, though encounters are less frequent due to their offshore habits. Peregrine falcons (Falco peregrinus) pose a significant risk during flight, using high-speed dives to capture birds in transit to or from colonies. Large , including great black-backed gulls, occasionally prey on adults at the surface or near nests, while (Ursus maritimus) represent a rare but severe threat in regions where colonies overlap with bear foraging areas. Razorbills employ behavioral adaptations to mitigate predation risks across life stages. Adults evade aerial predators by plunging into the water and diving to depths of up to 100 meters, using their streamlined bodies and wings for rapid underwater escape. For chicks, fledging involves a high-risk "jump" from cliff ledges—often 50–100 meters above the sea—where the semi-precocial young flutter down with whirring wings, accompanied by the male parent, to reach safer offshore waters and avoid land-based predators. Predation impacts are amplified in colonies with open or low-elevation nest sites, leading to higher losses compared to those using enclosed crevices or boulders, which razorbills preferentially select to reduce accessibility for predators like and foxes. In accessible sites, nest predation can contribute to up to 30% reproductive failure, influencing overall productivity and prompting shifts toward more secure breeding locations over time.

Anthropogenic threats

One of the primary anthropogenic threats to the Razorbill (Alca torda) is oil pollution from spills, which compromises the of their feathers, leading to loss of insulation, , impaired feeding, and high mortality rates. For instance, during the 1983 wreck event in , approximately 25,000 oiled and emaciated Razorbills washed ashore across Britain, , , , and the , with oil identified as a key contributing factor to their deaths. Similarly, the 2002 off resulted in the deaths of tens of thousands of alcids, including significant numbers of Razorbills, due to acute oiling effects. Bycatch in commercial fisheries represents another major ongoing risk, particularly entanglement in gillnets and driftnets, which causes direct mortality and population declines in vulnerable areas. In the North and Baltic Seas, Razorbills are among the seabirds frequently caught as during operations targeting like , exacerbating pressures from that reduces available prey stocks. Additionally, competition for such as , driven by intensive commercial harvesting, limits food availability and indirectly affects Razorbill efficiency. Climate change poses a growing by altering temperatures and prey distributions, which disrupts Razorbill breeding and . Rising surface temperatures have led to declines in key prey like sandeels, contributing to reduced productivity and lower fledging rates in regions such as the northeast . Recent studies indicate that warmer conditions and associated stormy have negatively impacted adult and breeding performance, with projections suggesting further declines in breeding across breeding colonies due to these bottom-up effects. In the , for example, phenological shifts linked to warming have altered demographic responses, potentially reducing reproductive output in affected populations. Habitat disturbance from human activities further endangers Razorbill colonies, including recreational , marine development, and historical practices like collecting. Tourism and activities such as offshore windfarm and aggregate can cause nest site abandonment through noise and visual disturbance, particularly in sensitive colony-nesting sites. collecting historically contributed to significant declines by removing breeding attempts, with past exploitation noted as a key factor in range contractions. The introduction of to breeding islands, often facilitated by human vectors, has also increased predation risks on eggs and chicks, compounding vulnerabilities. Historical persecution through for food and feathers severely depleted Razorbill populations until protective measures were enacted in the . Intensive harvesting of adults and eggs for subsistence and trade led to widespread declines across their range, with colonies in nearly extirpated by the late 1800s. In , legal hunting persists, with 2,000–200,000 birds taken annually, about 20% of which occurs illegally despite bans in other regions. These practices were curtailed by international protections, such as those under the Migratory Bird Treaty Act in , allowing partial recovery. Emerging infectious diseases, particularly highly pathogenic (HPAI) subtype H5N1, have emerged as a significant threat in recent years. The global outbreak from 2022 to 2024 caused mass mortality events among seabirds, including razorbills, across the North Atlantic and beyond, with unprecedented die-offs reported in and linked to spillover from and wild reservoirs.

Conservation

Status and populations

The Razorbill (Alca torda) is classified as Least Concern on the , with a global population trend that appears to be increasing overall. The European regional assessment classifies the population as Near Threatened. This global assessment, last updated in 2021, reflects stability or growth since earlier evaluations, though regional variations exist due to localized environmental pressures. The species does not meet thresholds for higher threat categories under criteria for , range, or decline rates. Global population estimates indicate approximately 838,000–1,660,000 mature individuals, equivalent to 1.26–2.49 million total individuals, with over 90% occurring in . Breeding pair estimates are around 700,000 globally, with roughly half in alone, which hosts the largest single concentration. In , the breeding population comprises 519,000–1,070,000 mature individuals. Regional trends show increases in key areas: 's population has grown significantly at major colonies like Látrabjarg since 2009, while has experienced rapid overall growth in recent decades. In contrast, eastern supports about 38,000 breeding pairs, with overall increases since the late but some localized declines linked to fishing and food shortages. Population monitoring relies on seabird atlases, colony censuses, and international reports, such as those from the International Council for the Exploration of the Sea (ICES) Working Group on Ecology, which track breeding success and abundance across the North Atlantic. These efforts, including the British Trust for Ornithology's Monitoring Programme, provide data on trends from 1986 onward. The species' , with individuals surviving up to 41–42 years in the wild, contributes to stability by allowing experienced breeders to persist through adverse conditions. However, the low reproductive rate—one chick per year per pair—limits recovery from mortality events, making the population vulnerable to episodic threats despite positive trends.

Management efforts

Razorbills are protected under the EU Birds Directive (Directive 2009/147/EC), which safeguards all wild bird species native to the , including their habitats and prohibiting deliberate killing or capture. In the United States, the species is covered by the Migratory Bird Treaty Act of 1918, which prohibits , taking, or possessing migratory birds without authorization. of Razorbills for meat, eggs, and feathers, once widespread, has been banned in many regions since the early 1900s through these and similar international agreements. However, regulated persists in , where 2,000–200,000 birds are killed annually under quotas, with efforts ongoing to reduce illegal takes and ensure ; direct exploitation has been significantly reduced overall. Site management efforts focus on protecting breeding colonies through predator control and ongoing monitoring. Invasive predators like rats have been eradicated from several key islands, leading to improved breeding success for Razorbills; for instance, successful rat removal on islands such as Ramsey in Wales has allowed seabird populations, including Razorbills, to rebound. Colony monitoring programs, such as those on Skomer Island in Wales, involve annual censuses and habitat assessments to track breeding pairs and identify environmental pressures. Pollution mitigation includes protocols for oil spill response tailored to seabirds, coordinated through international agreements like the African-Eurasian Waterbird Agreement (AEWA), which emphasizes rapid rehabilitation and habitat cleanup to minimize impacts on species like the Razorbill. To address bycatch in fisheries, the EU has promoted mitigation measures under its 2012 Plan of Action for reducing incidental catches of seabirds, with post-2020 efforts including requirements for gear modifications like weighted lines and bird-scaring devices in high-risk areas, though implementation varies by member state. Research initiatives employ GPS tracking to map ranges and migration patterns of individual Razorbills, revealing adaptations to changing prey distributions. Modeling studies assess prey availability under scenarios, aiding predictions of colony resilience by integrating oceanographic data with demographics. These efforts have contributed to recoveries in protected areas, with UK Razorbill colonies showing overall increases of around 18% since the late in monitored sites.

Evolutionary history

Fossil record

The genus Alca originated during the Miocene to Pliocene epochs, approximately 23 to 5 million years ago, with its early evolution centered in the basin. evidence indicates that the was already present in the , as suggested by specimens like Alca cf. torda from the St. Mary's Formation in , , dated to around 7.246 million years ago. This early diversification occurred primarily along North American and European coastal regions, reflecting adaptations to marine environments in the Atlantic. The fossil record of Alca includes several extinct species, highlighting greater morphological diversity than seen in the modern Razorbill. Alca minor, from Pliocene deposits, was characterized by a smaller bill compared to the extant A. torda, suggesting niche specialization in foraging or body size. In contrast, Alca grandis, known from early Pliocene sites such as the Yorktown Formation in (approximately 4.4 million years ago), was notably larger overall, with robust skeletal elements indicating a body size exceeding that of the modern species; this taxon became extinct by around 2 million years ago. These fossils, comprising thousands of specimens from Miocene and strata, underscore the genus's abundance in prehistoric Atlantic avifaunas. The earliest definitive remains of the modern Razorbill (Alca torda) date to the late Pleistocene, around 100,000 years ago, with specimens recovered from sites in Europe and North America. These fossils indicate that A. torda had established its range across the North Atlantic by this period, predating the Last Glacial Maximum. The genus Alca exhibited higher species diversity during the Pliocene, with at least six extinct taxa coexisting alongside early forms of the modern lineage, before a decline linked to climatic shifts at the Pliocene-Pleistocene boundary. Alca torda emerged as a post-glacial survivor, persisting through the Quaternary ice ages as the sole extant member of the genus, while most relatives went extinct. This pattern reflects broader trends in alcid evolution, where Atlantic clades experienced significant turnover during glacial-interglacial cycles.

Relationship to other auks

The Razorbill (Alca torda) belongs to the family Alcidae, which comprises 25 species of seabirds adapted to northern marine environments, including auks, murres, guillemots, puffins, and auklets. Within this family, the Razorbill is classified in the subfamily Alcinae, alongside murres (Uria spp.) and guillemots (Cepphus spp.), reflecting shared morphological and ecological traits such as pursuit diving and colonial breeding. This grouping highlights the Razorbill's position in a clade of northern hemisphere divers that evolved specialized wing and body structures for underwater foraging. The Razorbill's closest living relative is the dovekie (Alle alle), with genetic analyses placing the dovekie as the to the Razorbill- within the Alcini. Phylogenetic studies estimate the between the Razorbill and dovekie at approximately 10-15 million years ago, based on sequences that reveal early splits in alcid evolution. The extinct (Pinguinus impennis), which vanished in 1844 after the last confirmed pair was killed off , represents the Razorbill's nearest extinct relative in the sister Pinguinus. This close kinship is evident in molecular data supporting a shared ancestry within Alcini, distinct from other alcid subfamilies. Convergent evolution is prominent in the Razorbill's lineage, particularly contrasting the flightless with the flying Razorbill, both exhibiting adaptations for such as dense for insulation and robust wings for underwater. The 's body plan paralleled that of (Spheniscidae) in the , with independent of flightlessness and streamlined forms for efficient swimming, driven by similar selective pressures in cold, prey-rich seas—yet the Razorbill retained flight capability for migration and predator evasion. These shared diving traits across distant lineages underscore parallel adaptations in alcids and spheniscids, including reduced and enhanced pectoral musculature. Hybridization between Razorbills and common murres (Uria aalge) occurs rarely in mixed breeding colonies, typically involving attempted copulations without successful reproduction. Observations document social interactions and semen transfer in such attempts, but no fertile hybrids have been confirmed, likely due to behavioral barriers and genetic incompatibilities within Alcinae. Possible hybrid individuals have been reported morphologically, yet breeding failure limits between these species. The Razorbill exhibits , with its distribution confined to the from boreal to low-Arctic waters, lacking any Pacific counterparts in the genus Alca. This biogeographic pattern stems from historical barriers like the , which prevented post-Miocene dispersal of Alca ancestors from the Atlantic around into Pacific basins, unlike more mobile alcid genera. Fossil evidence briefly references shared ancestors with Pacific alcids, but the Razorbill's lineage remained isolated in the Atlantic.

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