Razorbill
Razorbill | |
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On Skomer Island, Pembrokeshire, Wales , Wales
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Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Charadriiformes |
Family: | Alcidae |
Genus: | Alca |
Species: | A. torda
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Binomial name | |
Alca torda | |
Subspecies[1] | |
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The razorbill, razor-billed auk,
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,[5] oil spills,[6] and deterioration of food quality. The IUCN records the population of the species as fluctuating,[7] causing its status to interchange. It has been recorded that the population had increased from 2008 to 2015,[8] decreased from 2015 to 2021,[9] and appears to be increasing or stable at the present. It is believed the population of the Razorbill lies between 838,000 and 1,600,000 individuals.
Taxonomy
The genus Alca was introduced in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae.[10] The genus name Alca is from Norwegian Alke, and torda is from törd a Gotland Swedish dialect word. Both terms refer to this species.[11] The word Alca had been used by earlier authors for the razorbill such as Carolus Clusius in 1605[12] and Francis Willughby in 1676.[13]
The razorbill (Alca torda) is now the sole species in the genus Alca.[14] 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).[15]
There are two subspecies of razorbill recognized by the
Image | Subspecies | Distribution |
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Alca torda torda Linnaeus 1758 | the . | |
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.
Description
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
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%.[19] 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.[20]
Distribution and habitat
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
Some 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.[23]
- Runde, Norway (62°24' N) - 3,000 pairs
- St Kilda
- Staple Island, Outer Farne Islands, UK (55°38' N) - 20,000 pairs, breeding season May to mid-July.
- Bempton Cliffs, [Flamborough and Filey Coast Special Protection Area]United Kingdom (54°14’ N) - 20,000 pairs from March to mid-July.
- Skomer Island, Pembrokeshire, Wales
- Heligoland, Germany (54°10' N) - near the southern limit in Europe, a few pairs only
- Gannet Islands, Canada (53°58' N) - 9,800 pairs[24]
- 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)
Behaviour
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. [25]
During breeding, both males and females protect the nest. Females select their mate and will often encourage competition between males before choosing a partner.[26] Once a male is chosen, the pair will stay together for life.
Reproduction
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.[17] 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.[17] The pair will mate up to 80 times in a 30-day period to ensure fertilization.[27] Females will sometimes encourage other males to engage in copulation to guarantee successful fecundity.[26]
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 sites
Nest site choice is very important for these birds to ensure the protection of the young from predators. Unlike
The mating pair will often reuse the same site every year.[29][30] 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.[31] Nest under a boulder, rarely on an exposed ledge, may use Puffin or rabbit burrow.[32] Although gregarious in breeding colonies, nests are not contiguous, but some meters apart, resulting in less aggression than in Guillemot colonies.[32]
Incubation and hatching
Females lay a single egg per year, usually from late April to May. The egg is an
Feeding
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.[35] 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.[36]
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.[17] Females will generally feed their chicks more frequently than males.[36] 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.[23]
Diet
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
Predators
The adult razorbill has several predators which include:
Razorbill eggs were collected until the late 1920s in
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.[17] 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
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.[39] 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
References
- ^ Gill F, D Donsker & P Rasmussen (Eds). 2020. IOC World Bird List (v10.2). doi : 10.14344/IOC.ML.10.2.
- ^ American Ornithologists' Union (1931), A Check-List of North American Birds (4th ed.), Lancaster, PA: Lancaster Press, p. 144
- ISBN 9781248434567
- PMID 12200471.
- S2CID 216173366. Retrieved 6 September 2018.
- ^ Leopold, Mardik (January 2004). "The Tricolor oil spill: Characteristics of seabirds found oiled in the Netherlands".
- . Retrieved 31 December 2021.
- ^ "Razorbill". IUCN Red List. Archived from the original on 19 August 2023. Retrieved 19 August 2023.
- ^ "IUCN Red List of Threatened Species". Iucnredlist.org. Retrieved 10 August 2022.
- ^ Linnaeus, Carl (1758). Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis (in Latin). Vol. 1 (10th ed.). Holmiae (Stockholm): Laurentii Salvii. p. 130.
- ISBN 978-1-4081-2501-4.
- ^ Clusius, Carolus (1605). Exoticorum libri decem. Lugdunum Batavorum [Leiden]: Ex Officinâ Plantinianâ Raphelengii. p. 367.
- ^ Willughby, Francis (1676). Ornithologiae libri tres (in Latin). London: John Martyn. p. 243.
- Rasmussen, Pamela, eds. (July 2021). "Noddies, gulls, terns, skimmers, skuas, auks". IOC World Bird List Version 11.2. International Ornithologists' Union. Retrieved 16 August 2021.
- PMID 8587501.
- ^ "Razorbill Fact Sheet". Lincoln Park Zoo. Archived from the original on 29 September 2011.
- ^ a b c d e Conder, P.J. (1950). "On the courtship and social displays of three species of auk". British Birds. 43: 65–69.
- ISBN 978-0198540328.
- doi:10.1139/Z07-113.
- ^ McCarthy, Michael (10 July 2008). "Seabird Born in Summer of Love Still Breeding in Wales". The Independent. London. Retrieved 10 July 2008.
- S2CID 244752949.
- ^ Lavers, J.L.; Hipfner, M.J.; Chapdelaine, G.C. (2009). The Birds of North America. Vol. 16. Philadelphia, PA: The Birds of North America, Inc.
- ^ S2CID 29136400.
- ^ Chapdelaine, G.; Diamond, A.W.; Elliot, R.D.; Robertson, G.J. (2001). Status and population trends of the Razorbill in eastern North America (Report). Occasional Paper. Canadian Wildlife Service.
- ^ "Razorbill=29 December 2022". audubon.
- ^ JSTOR 4534962.
- JSTOR 4088369.
- ^ Plumb, W.J. (1965). "Observations on the breeding biology of the Razorbill" (PDF). British Birds. 58 (11): 449–456.
- .
- ^ a b Lavers, J.L.; Jones, I.L. (2007). "Factors affecting rates of intraspecific kleptoparasitism and breeding success of the Razorbill at the Gannet Islands, Labrador" (PDF). Marine Ornithology. 35 (1): 1–7.
- ^ Williams, A.J. (1971). "Laying and nest-building behavior in the larger auks (Aves, Alcidae)". Astarte. 4: 61–67.
- ^ ISBN 0-19-850187-0.
- ^ Ralph, C. John; Hunt Jr., George L.; Raphael, Martin G.; Piatt, John F., eds. (1995). Ecology and Conservation of the Marbled Murrelet (Report). Vol. PSW-152. Albany, California: USDA Forest Service.
- S2CID 164436494.
- JSTOR 4086771.
- ^ .
- .
- ^ The Daily Mail April 18 1930: article by Susan Rachel Ferguson
- ISBN 0-9533553-0-6.
- ISBN 0-12-515671-5.
External links
- Explore Species: Razorbill at eBird (Cornell Lab of Ornithology)
- Razorbill photo gallery at VIREO (Drexel University)
- Interactive range map of Alca torda at IUCN Red List maps
- Audio recordings of Razorbill on Xeno-canto.