- North-West Atlantic Ocean species (NWARMS)
The Razorbills are found in boreal and sub-Arctic waters of the Atlantic. Razorbills are exclusively an Atlantic species, with no counterpart in the North Pacific. It breeds between 73 degree north and 43 degree north from Hudson Strait and west Greenland south to the Gulf of Maine, and from Iceland Jan Mayen, Bjornoya and northwest Russia (White Sea), south to Brittany and the Baltic Sea. During the winter they are mostly offshore in northern boreal water south to Long Island, Azores and western Mediterranean. Their breeding colonies can be found on sea cliffs of Canada, Maine, Greenland, Iceland, Jan Mayen, Faeroe Island, Britain, Ireland, Brittany, France, Helgland, Germany, Denmark, Sweden, Finland, Norway, Bjornoya, Kola Peninsula and White Sea. (Nettleship & Birkhead, 1985)
Biogeographic Regions: arctic ocean (Native ); atlantic ocean (Native )
occurs (regularly, as a native taxon) in multiple nations
Regularity: Regularly occurring
Type of Residency: Year-round
Regularity: Regularly occurring
Type of Residency: Breeding
Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDS: Hudson Strait and western Greenland south to Gulf of Maine, and from Iceland, Jan Mayen, Bjornoya and northwestern Russia south to Brittany and the Baltic Sea. In the early 1980s, nested on four islands in Gulf of Maine (Maine, the only U.S. breeding sites) (Spendelow and Patton 1988). WINTERS: mostly offshore in northern boreal waters south to Long Island (New York), Azores, western Mediterranean (AOU 1983).
Razorbills are heavy-billed auks with an unusually long, rather graduated tail. During summer the head and the throat of adult Razorbills are black and dark chocolate brown. The under parts, including the under wing coverts, are white. There is a narrow white line extending forward from the eyes to the top of the bill. The gape is bright yellow and its iris is dark brown. Their legs and feet are black.
During winter the adult Razorbills are in their breeding plumage, but their throat, sides of neck, and face behind the eye are white. The vertical white line on the head and bill is less prominent.
The average weight for female Razorbills ranged from 505g to 730g. For males the weight ranged from 530g-720g. Average wing length for females ranged from 183mm-210mm. For males the wing length ranged from 182mm-206mm. (Wagner, 1999)
Range mass: 505 to 730 g.
Range wingspan: 182 to 210 mm.
Length: 43 cm
Weight: 719 grams
Habitat and Ecology
Razorbill colonies occur on cliffs and offshore islands. They breed colonially in rocky, coastal regions on mainland cliffs and on offshore islands. In most areas breeding locations are situated in boulder screens or on cliff-faces in rock crevices or on ledges. Because the chicks cannot fly when they leave the colony, the breeding site must give immediate access to the sea. They feed in continental shelf waters, and usually feed rather close to shore than Common Murres (Uria aalge). Sometimes, Razorbills scatter among the Murres. (Gaston & Jone, 1998)
Habitat Regions: saltwater or marine
Aquatic Biomes: coastal
Water temperature and chemistry ranges based on 14894 samples.
Depth range (m): 0 - 0
Temperature range (°C): -0.858 - 24.405
Nitrate (umol/L): 0.348 - 16.868
Salinity (PPS): 5.715 - 35.801
Oxygen (ml/l): 4.763 - 8.711
Phosphate (umol/l): 0.142 - 0.890
Silicate (umol/l): 0.565 - 12.889
Temperature range (°C): -0.858 - 24.405
Nitrate (umol/L): 0.348 - 16.868
Salinity (PPS): 5.715 - 35.801
Oxygen (ml/l): 4.763 - 8.711
Phosphate (umol/l): 0.142 - 0.890
Silicate (umol/l): 0.565 - 12.889
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.
Comments: Sea coasts and open sea. Nests on coastal cliffs and on rocky shores and islands, usually in crevice or niche or in holes between and under boulders (AOU 1983, Harrison 1978). Usually nests with murres (Terres 1980). Usually uses same nest site in successive years. Isolated islands free of quadruped predators seem essential for successful reproduction (Buckley and Buckley 1984).
Stellwagen Bank Pelagic Community
The species associated with this page are major players in the pelagic ecosystem of the Stellwagen Bank National Marine Sanctuary. Stellwagen Bank is an undersea gravel and sand deposit stretching between Cape Cod and Cape Ann off the coast of Massachussets. Protected since 1993 as the region’s first National Marine Sanctuary, the bank is known primarily for whale-watching and commercial fishing of cod, lobster, hake, and other species (Eldredge 1993).
Massachusetts Bay, and Stellwagen Bank in particular, show a marked concentration of biodiversity in comparison to the broader coastal North Atlantic. This diversity is supported from the bottom of the food chain. The pattern of currents and bathymetry in the area support high levels of phytoplankton productivity, which in turn support dense populations of schooling fish such as sand lance, herring, and mackerel, all important prey for larger fish, mammals, and seabirds (NOAA 2010). Sightings of many species of whales and seabirds are best predicted by spatial and temporal distribution of prey species (Jiang et al 2007; NOAA 2010), providing support for the theory that the region’s diversity is productivity-driven.
Stellwagen Bank is utilized as a significant migration stopover point for many species of shorebird. Summer visitors include Wilson’s storm-petrel, shearwaters, Arctic terns, and red phalaropes, while winter visitors include black-legged kittiwakes, great cormorants, Atlantic puffins, and razorbills. Various cormorants and gulls, the common murre, and the common eider all form significant breeding colonies in the sanctuary as well (NOAA 2010). The community of locally-breeding birds in particular is adversely affected by human activity. As land use along the shore changes and fishing activity increases, the prevalence of garbage and detritus favors gulls, especially herring and black-backed gulls. As gull survivorship increases, gulls begin to dominate competition for nesting sites, to the detriment of other species (NOAA 2010).
In addition to various other cetaceans and pinnipeds, the world’s only remaining population of North Atlantic right whales summers in the Stellwagen Bank sanctuary. Right whales and other baleen whales feed on the abundant copepods and phytoplankton of the region, while toothed whales, pinnipeds, and belugas feed on fish and cephalopods (NOAA 2010). The greatest direct threats to cetaceans in the sanctuary are entanglement with fishing gear and death by vessel strikes (NOAA 2010), but a growing body of evidence suggests that noise pollution harms marine mammals by masking their acoustic communication and damaging their hearing (Clark et al 2009).
General threats to the ecosystem as a whole include overfishing and environmental contaminants. Fishing pressure in the Gulf of Maine area has three negative effects. First and most obviously, it reduces the abundance of fish species, harming both the fish and all organisms dependent on the fish as food sources. Secondly, human preference for large fish disproportionately damages the resilience of fish populations, as large females produce more abundant, higher quality eggs than small females. Third, by preferentially catching large fish, humans have exerted an intense selective pressure on food fish species for smaller body size. This extreme selective pressure has caused a selective sweep, diminishing the variation in gene pools of many commercial fisheries (NOAA 2010). While the waters of the SBNMS are significantly cleaner than Massachusetts Bay as a whole, elevated levels of PCBs have been measured in cetaceans and seabird eggs (NOAA 2010). Additionally, iron and copper leaching from the contaminated sediments of Boston Harbor occasionally reach the preserve (Li et al 2010).
- Clark CW, Ellison WT, Southall BL, Hatch L, Van Parijs SM, Frankel A, Ponirakis D. 2009. Acoustic masking in marine ecosystems: intuitions, analysis and implication. Inter-Research Marine Ecology Progress Series 395:201-222.
- Eldredge, Maureen. 1993. Stellwagen Bank: New England’s first sanctuary. Oceanus 36:72.
- Jiang M, Brown MW, Turner JT, Kenney RD, Mayo CA, Zhang Z, Zhou M. Springtime transport and retention of Calanus finmarchicus in Massachusetts and Cape Cod Bays, USA, and implications for right whale foraging. Marine Ecology 349:183-197.
- Li L, Pala F, Mingshun J, Krahforst C, Wallace G. 2010. Three-dimensional modeling of Cu and Pb distributions in Boston Harbor, Massachusetts and Cape Cod Bays. Estuarine Coastal & Shelf Science. 88:450-463.
- National Oceanographic & Atmospheric Administration. 2010. Stellwagen Bank National Marine Sanctary Final Management Plan and Environmental Assessment. “Section IV: Resource States” pp. 51-143. http://stellwagen.noaa.gov/management/fmp/pdfs/sbnms_fmp2010_lo.pdf
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Arrives in southern breeding areas (Maine) near end of February (Cowger 1976). Birds breeding in Labrador and Greenland migrate to Newfoundland and farther south (Brown 1985).
In general, adult Razorbills mainly feed on mid-water schooling fish: capelin, sandlance (Ammodytes), herrings (Clupea harengus), sprats (Sprattus sprattus), and juvenile cod. However, the species of the fish vary regionally. Adult Razorbills wintering off Newfoundland feed mainly on crustaceans. In Labrador the diet of adult Razorbills early in the season is largely capelin, but after the chicks hatch the adult take only some capelin but large numbers of small Myxocephalus sculpins and euphausiids. (Nettleship & Birkhead, 1985)
For the chicks, the parents usually bring one to six fish at a meal. Only occasionally do they bring up to 20 fish. Yet, the number of fish brought in a meal decreases as their size increases. The parents hold the fish crosswise in the bill to feed the chicks. Average length of fish brought to chicks varies in different regions. Sandlances that were brought to chicks in Irish Sea colonies were 53-79mm, yet, in Labrador they were 137mm. The diet of young Razorbills after they leave the colony is not known. (Nettleship & Birkhead, 1985)
Primary Diet: carnivore (Piscivore )
Comments: Winter adult diet off Newfoundland mainly crustaceans, mainly fishes in Baltic. Summer adult diet in Labrador: capelin, sculpins, euphausiids. In southeastern Canada, chicks are fed fishes (mainly sandlance and capelin). Dives to at least 120 m (Piatt and Nettleship 1985).
Razorbills are carnivores (eating vertebrates) that are also eaten by other carnivores.
Most auk chicks are vulnerable to predation from gulls during fledging. Razorbill chicks fledging asynchronously, either fairly early in the morning or late in the evening, are not protected. Therefore, they were more likely to be killed by gulls than those fledging synchronously. In other words, Razorbill chicks fledging not at the same time/rate are easier prey for gulls. (Nettleship & Birkhead, 1985)
Razorbills provide relatively large nutritious eggs, high in fat, having larger yolks than those of most terrestrial birds, as a result, they are easily targeted by red fox, raven and other predators. (Gaston & Jones, 1998)
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 21 - 300
Comments: Many small colonies, but a major portion of the global population (over 200,000) nest in one large colony at western tip of Iceland.
Comments: World population was estimated at about 700,000 pairs by Nettleship and Evans (1985). Censuses during the 1970s and early 1980s yielded about 15,000 pairs breeding in Canada/New England. See Evans (1984) for population data from Greenland.
Annual adult survival in each of several areas was > 80%; usually 89% or more (Hudson 1985).
Life History and Behavior
Razorbill chicks hatch at a weight of about 60g, and weight is directly correlated with egg size. They spend about 18 days at the breeding site. Chicks leave the colony around 18-23 days after hatching. By that time they are only partly grown and still flightless. They weigh between 140g and 180g when they leave the colony. (Wagner, 1999)
Status: wild: 29.4 (high) years.
Status: wild: 88 months.
Lifespan, longevity, and ageing
Egg-laying for Razorbills start in the first week of May and laying continues until the first week of June. At higher latitudes, or where water temperatures are lower, laying is later. A female Razorbill can produce only one egg each season. Most breeding sites are enclosed or partially enclosed to protect the egg from predators. The single egg is usually laid directly on bare rock, but some parents would collect small stones, dried dropping, lichen or other bits of vegetation from the immediate surrounding area and place them where the egg will be laid. (Nettleship & Birkhead, 1985)
Before laying their eggs, at least half of the females leave their mates and sneak off to another ledge to copulate with other males. Then they come back and copulate with their mates on an average of 80 times in the 30 days before the laying of the first egg. Later, while their mates are safely occupied incubating their eggs, the females slip away again to the neighboring ledge for more copulation. The couplings are like auditions to see who is better and are probably important in pair formation. (Carely, 1993)
Range eggs per season: 1 (high) .
Average eggs per season: 1.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
Average time to hatching: 36 days.
Average eggs per season: 1.
Incubation for some happens immediately after laying. Parents exchange incubation duty several times a day. After the chick hatched the parents would feed the chick with fish up to 20 fish at a time, but they usually bring one to six fish at a meal. (Nettleship & Birkhead, 1985)
Parental Investment: male parental care ; female parental care
Eggs are laid in May in Maine, June where seas are colder. Clutch size is 1. Incubation, by both sexes, averages 35-37 days. Single young is tended by both sexes, leaves for sea at average age of 17-19 days, tended by male for several weeks. In Wales, first breeds at 4-5 years.
Molecular Biology and Genetics
Statistics of barcoding coverage: Alca torda
Public Records: 11
Specimens with Barcodes: 12
Species With Barcodes: 1
Barcode data: Alca torda
There are 11 barcode sequences available from BOLD and GenBank. Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species. See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
IUCN Red List Assessment
Red List Category
Red List Criteria
After declining in the Gulf of St Lawrence during the 1970s, the species increased in the 1980s and is probably now as abundant as it has been in this century. The population of Britain and Ireland increased from 1970-1985, yet, the extent of increase is not known. (Gaston & Jones, 1998)
US Migratory Bird Act: no special status
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Status in Egypt
National NatureServe Conservation Status
Rounded National Status Rank: N4B,N4N : N4B: Apparently Secure - Breeding, N4N: Apparently Secure - Nonbreeding
Rounded National Status Rank: N1B - Critically Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G5 - Secure
Reasons: Widely distributed, although the bulk of the world population breeds in a few colonies in Iceland. Despite historic declines, global population thought to be stable or increasing at present.
Global Short Term Trend: Relatively stable (=10% change)
Comments: Thought to be stable or increasing throughout major parts of range (Hipfner and Chapdelaine 2002). Hyslop and Kennedy (1992) indicated population increases in most areas of the Gulf of St. Lawrence and estuary between the 1970s and 1990. Populations increased in the Gulf of St. Lawrence region in the 1980s according to Chapdelaine and Brousseau (1992). Recolonization continues in Gulf of Maine as population increases (Podolsky 1989, Mawhinney and Sears 1996).
Global Long Term Trend: Decline of 30-70%
Comments: Hunting, egging and persecution have caused marked reductions in populations, but there have been no large-scale changes to range over historical period (Hipfner and Chapdelaine 2002). Gulf of St. Lawrence populations have declined over long term (Nettleship and Evans 1985).
Comments: Populations in Greenland may be impacted by hunting and salmon netting (Evan 1984). On islands off Labrador, breeding populations were eliminated or reduced by colonizing arctic foxes (Birkhead and Nettleship 1995).
Management Requirements: See Evans and Nettleship (1985) for management recommendations.
Management Research Needs: See Evans and Nettleship (1985) for research recommendations.
Relevance to Humans and Ecosystems
Economic Importance for Humans: Positive
Ornithologists are studying the sexual behaviors among razorbills. They are/very likely to use Razorbill as a model to study avian mating behavior. (Carey, 1993)
Positive Impacts: research and education
Comments: Hunted on breeding grounds in Greenland (Evans 1984).
The Razorbill (Alca torda) is a colonial seabird that only comes to land in order to breed. This agile bird chooses 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. Once the chick has hatched, the parents take turns foraging for their young and sometimes fly long distances before finding prey.
The Razorbill is primarily black with a white underside. The male and female are identical in plumage; however, males are generally larger than females. In 1918, the Razorbill was protected in the United States by the Migratory Bird Treaty Act. Presently, the major threat for the population is the destruction of breeding sites.
The Razorbill has white underparts and a black head, neck, back and feet during 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 nonbreeding season, the throat and face behind the eye become white, and the white line on the face becomes less prominent. The thick black bill has a blunt end. It is large for an alcid and its mean weight ranges from 505 to 890 g (17.8 to 31.4 oz). The female and male adults are very much alike, having only small differences such as wing length. The wing length of adult males ranges from 201–216 mm (7.9–8.5 in) while that of females ranges from 201 to 213 mm (7.9 to 8.4 in). 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. The Razorbill chooses one partner for life, and nests along coastal waters of the continental shelf. 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 89-95%. Though the Razorbill's average lifespan is roughly 13 years, a bird ringed in the UK in 1967 has survived for at least 41 years — a record for the species.
The razorbill is in the family Alcidae and its genus is Alca. It is closest living relative to the Great Auk (Pinguinis impennis) which is now extinct. The Alcini clade also includes the Common Murre (Uria aalge), the Thick-billed Murre (Uria lomvia) and the Dovekie (Alle alle).
There are two subspecies of Razorbill recognized by the American Ornithologists' Union. Alca torda torda, named by Linnaeus in 1758, occurs in the Baltic and White Seas, Norway, Bear Island, Iceland, Greenland, and eastern North America. Alca torda islandica was named by C. L. Brehm in 1831 and occurs throughout the British Isles 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.
Habitat and distribution
The world population of Razorbills is estimated at about 500,000 to 700,000 breeding pairs. Razorbills thrive in water surface temperature below 15°C. They are often seen with other larger auks, such as the 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 some moving south as far as the western Mediterranean. Approximately 60 to 70 percent of the entire razorbill population breeds in Iceland. Razorbill colonies include (north to south):
- Grímsey, Iceland (66°33' N)
- Látrabjarg, Iceland (65°30' N) - 230,000 pairs, about 40% of the global population (mid-1990s estimate). Breeding season June - July.
- Runde, Norway (62°24' N) - 3,000 pairs
- Staple Island, Outer Farne Islands, UK (55°38' N) - breeding season May to mid-July.
- Heligoland, Germany (54°10' N) - near southern limit in Europe, a few pairs only
- Gannet Islands, Canada (53°58' N) - 9,800 pairs (Chapdelaine et al. 2001)
- Funk Island, Canada (49°45' N)
- Baccalieu Island, Canada (48°07' N)
- Witless Bay, Canada (47°13' N)
- Cape St. Mary's, Canada (46°49' N)
The life history traits of the razorbill are similar to that of the Common Murre. However, Razorbills are slightly more agile. During breeding, both male and female protect the nest. Females select their mate and will often encourage competition between males before choosing a partner. 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. 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. The pair will mate up to 80 times in a 30 day period to ensure fertilization. Females will sometimes encourage other males to engage in copulation to guarantee successful fecundity.
Throughout the pre-laying period Razorbills will socialize in large numbers. There are two types of socializing that occur. Large groups will dive and swim together in circles repeatedly and all rise up to the surface, heads first and bills open. Secondly, large groups will swim in a line weaving across each other in the same direction.
Nest sites and location
Nest site determination is very important for these birds to ensure protection of young from predators. Unlike murres, nest sites are not immediately alongside the sea on open cliff ledges but at least 10 cm 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. Content-Type:ting pair will often reuse the same site every year. Since chicks do not have the ability to fly nests close to 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 eggs.
Incubation and hatching
Females lay a single egg per year. The egg is an ovoid-pyramoidal shape, ground in color and has dark brown blotches. Incubation occurs 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. 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 male parent will accompany the chick to sea.
Razorbills dive deep into the sea using their wings and their streamlined bodies to propel themselves toward their prey. While diving, they rarely stay in groups, but rather spread out to feed. The majority of their feeding occurs at a depth of 25 meters but they have the ability to dive up to 120 meters below the surface. During a single dive an individual can capture and swallow many schooling fish, depending on their size. Razorbills spend approximately 44.0 percent of their time foraging at sea. 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. Females will generally feed their chicks more frequently than males. They may well fly more than 100 km out to sea to feed when during egg incubation, but when provisioning the young, they forage closer to the nesting grounds, some dozen kilometers away, and often in shallower water.
The diet of a Razorbill is very similar to that of a Common Murre. 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 
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 an adult razorbill to avoid predation is by diving. Arctic Foxes can also predate significant numbers of adults, eggs, and chicks in some years 
Conservation and management
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. Other threatening interactions include oil pollution which can damage breeding sites. Any damage to breeding sites can reduce possible nest sites and affect 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
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. A number of fossil forms have been found:
- Alca "antiqua" (Late Miocene/Early Pliocene of Lee Creek Mine, USA)[verification needed]
- Alca sp. (Late Miocene/Early Pliocene of Lee Creek Mine, USA) - possibly A. stewarti
- Alca stewarti (Kattendijk Sands Early Pliocene of Belgium)
- Alca ausonia (Yorktown Early Pliocene of Lee Creek Mine, USA - 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.
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- Plumb, W. J., "Observations on the breeding biology of the Razorbill", British Birds 58: 449-4.120
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- Lavers, J.L.; Jones, I.L. (2007), "Factors affecting rates of intraspecific kleptoparasitism and breeding success of the Razorbill at the Gannet Islands, Labrador", Marine Ornithology 35: 1–7
- Williams, A. J. (1971), Laying and nest-building behavior in the larger auks(Aves, Alcidae) 4, Astarte, pp. 61–67
- Ralph, John C. (1995), Ecology and Conservation of the Marbled Murrelet, PSW-152, Albany, California: USDA Forest Service Gen. Tech. Rep
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- Lavers, J.L.; Jones, I.L.; Robertson; Diamond, A.W. (20097), "Contrasting population trends at two Razorbill colonies in Atlantic Canada: additive effects of fox predation and hunting mortality?", Avian Conservation and Ecology 4: 3–17
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