Editing Razorbill

{{Use dmy dates|date=August 2023}}
{{Short description|Species of auk}}
{{Other uses}}
{{Speciesbox
| image = Razorbill with a nice catch.jpg
| image_caption = On [[Stora Karlsö]], [[Gotland]], Sweden [[File:Razorbill (Alca torda) (W1CDR0001424 BD7).ogg|thumb|center|Pair of Razorbills calling, recorded on [[Skokholm]], Wales]]
| status = LC
| status_system = IUCN3.1
| status_ref = <ref name="IUCN (Global)">{{cite iucn |author=BirdLife International. |year=2021 |errata=2023 |title=''Alca torda'' |volume=2021 |page=e.T22694852A228697220 |doi=10.2305/IUCN.UK.2021-3.RLTS.T22694852A228697220.en |access-date=18 April 2024}}</ref> (Global)
| status2 = LC
| status2_system = IUCN3.1
| status2_ref = <ref name="IUCN (Europe)">{{cite iucn |author=BirdLife International. |year=2021 |title=''Alca torda'' (Europe assessment) |volume=2021 |page=e.T22694852A166289520 |doi=10.2305/IUCN.UK.2021-3.RLTS.T22694852A166289520.en |access-date=18 April 2024}}</ref> (Europe)
| genus = Alca
| parent_authority = 
| species = torda
| authority = [[Carl Linnaeus|Linnaeus]], [[10th edition of Systema Naturae|1758]]
| subdivision_ranks = Subspecies
| subdivision_ref = <ref>Gill F, D Donsker & P Rasmussen (Eds). 2020. IOC World Bird List (v10.2). doi : 10.14344/IOC.ML.10.2.</ref>
| subdivision =
* ''A. t. torda'' - Linnaeus, 1758
* ''A. t. islandica'' - Brehm, CL, 1831
| range_map = Alca torda map.svg
}}

The '''razorbill''' ('''''Alca torda''''') is a North Atlantic colonial [[seabird]] and the only extant member of the [[genus]] ''[[Alca (bird)|Alca]]'' of the family [[Alcidae]], the [[auk]]s. It is the closest living relative of the extinct [[great auk]] (''Pinguinus impennis'').<ref name="Moum">{{cite journal |last=Moum |first=Truls |author2=Arnason, Ulfur |author3=Árnason, Einar |title=Mitochondrial DNA sequence evolution and phylogeny of the Atlantic Alcidae, including the extinct Great Auk (''Pinguinus impennis'') |journal=Molecular Biology and Evolution |volume=19 |issue=9 |pages=1434–1439 |year=2002 |publisher=[[Oxford University Press]] |location=Oxford |pmid=12200471 |doi=10.1093/oxfordjournals.molbev.a004206}}</ref> Historically, it has also been known as "auk",<ref name=Lockwood>{{cite book | last=Lockwood | first=William Burley  | author-link=William Burley Lockwood | date=1984 | title=The Oxford Dictionary of British Bird Names | location=Oxford | publisher=Oxford University Press | isbn=0-19-214155-4 }}</ref> "razor-billed auk"<ref name=AOU1931>{{Citation| author = American Ornithologists' Union | title = A Check-List of North American Birds | place = Lancaster, PA | publisher = Lancaster Press | year = 1931 | edition = 4th | page = 144 | language = English | url = https://archive.org/details/checklistofnorth1931amer/page/144/mode/2up }}</ref> and "lesser auk".<ref>''Proceedings of the Society of Antiquaries of Scotland, Volume 13'' (Edinburgh: Society of Antiquaries of Scotland, 1879), {{ISBN|9781248434567}}</ref>

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 [[Monogamy in animals|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,<ref>{{Cite journal |url=https://birdsna.org/Species-Account/bna/species/razorb/introduction |title=Razorbill - Introduction - Birds of North America Online |last1=Lavers |first1=Jennifer |last2=Hipfner |first2=J. Mark |last3=Chapdelaine |first3=Gilles |date=28 October 2009 |journal=Birds of the World |doi=10.2173/bow.razorb.01 |s2cid=216173366 |language=en |access-date=2018-09-06|url-access=subscription }}</ref> oil spills,<ref>{{cite web|url= https://www.researchgate.net/publication/228497510|title= The Tricolor oil spill: Characteristics of seabirds found oiled in the Netherlands|date= January 2004|volume= 6|last1= Leopold|first1= Mardik}}</ref> and deterioration of food quality. The IUCN records the population of the species as fluctuating,<ref name="IUCN (Global)"/> causing its status to interchange. It has been recorded that the population had increased from 2008 to 2015,<ref name="IUCN (Global) (2009)">{{Cite IUCN|title=''Alca torda'' (Razorbill)|author=BirdLife International|date=1 May 2009|page=e.T22694852A23088501|archive-date=19 August 2023|archive-url=https://web.archive.org/web/20230819055950/https://www.iucnredlist.org/species/22694852/23088501|access-date=18 April 2024}}</ref> decreased from 2015 to 2021,<ref name="IUCN (Global) (2015)">{{Cite IUCN|title=''Alca torda'' (Razorbill)|author=BirdLife International|date=1 October 2015|page=e.T22694852A82978388|doi=10.2305/IUCN.UK.2015-4.RLTS.T22694852A82978388.en|archive-url=https://archive.today/20240418172006/https://www.iucnredlist.org/species/22694852/82978388|archive-date=18 April 2024|access-date=18 April 2024}}</ref> and appears to be increasing or stable at the present.<ref name="IUCN (Global)"/> It is estimated that the current global razorbill population lies between 838,000 and 1,600,000 individuals.<ref name="IUCN (Global)"/> In 1918, the razorbill was protected in the United States by the [[Migratory Bird Treaty Act of 1918|Migratory Bird Treaty Act]]. 

== Taxonomy ==
[[File:Razorbill (Alca torda) in flight.jpg|thumb|In flight off [[Skomer Island]]]]
The [[genus]] ''Alca'' was formally described in 1758 by the Swedish naturalist [[Carl Linnaeus]] in the [[10th edition of Systema Naturae|tenth edition]] of his ''[[Systema Naturae]]''.<ref name=Linnaeus>{{cite book | last=Linnaeus | first=Carl | author-link=Carl Linnaeus | year=1758 | title= Systema Naturae per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis | volume=1 | edition=10th | page=130 | publisher=Laurentii Salvii | location=Holmiae (Stockholm) | language=Latin | url=https://www.biodiversitylibrary.org/page/727035 }}</ref> The genus name ''Alca'' is from Norwegian ''Alke'', and ''torda'' is from ''törd'' a [[Gotland]] Swedish dialect word; both terms refer to this species.<ref name=job>{{cite book |last=Jobling |first=James A |year=2010 |title=The Helm Dictionary of Scientific Bird Names |url=https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling |publisher=Christopher Helm |location=London |isbn=978-1-4081-2501-4 |pages=[https://archive.org/details/Helm_Dictionary_of_Scientific_Bird_Names_by_James_A._Jobling/page/n39 39], 388}}</ref> The [[type (biology)|type locality]] is [[Stora Karlsö]], just off the west coast of Gotland, Sweden.<ref name = HBW>{{Cite book | editor-first = Josep | editor-last = del Hoyo | editor2-first = Andrew | editor2-last = Elliott | editor3-last = Sargatal | editor3-first = Jordi | title = [[Handbook of the Birds of the World]]. Volume 3, Hoatzin to Auks | year = 1996 | page = 711 | place = Barcelona | publisher = Lynx Edicions | isbn = 84-87334-20-2 }}</ref>  The word ''Alca'' had been used for the razorbill by earlier authors such as [[Carolus Clusius]] in 1605<ref>{{ cite book | last=Clusius | first=Carolus | author-link=Carolus Clusius | date=1605 | title=Exoticorum libri decem | location=Lugdunum Batavorum [Leiden] | publisher=Ex Officinâ Plantinianâ Raphelengii | page=367 | url=https://www.biodiversitylibrary.org/page/8066435 }}</ref> and [[Francis Willughby]] in 1676.<ref>{{ cite book | last=Willughby | first=Francis | author-link=Francis Willughby | year=1676 | title=Ornithologiae libri tres | language=Latin | location=London | publisher=John Martyn | page=243 | url=https://www.biodiversitylibrary.org/page/56923623 }}</ref>

The razorbill (''Alca torda'') is now the sole species in the genus ''Alca'',<ref name=ioc>{{cite web| editor1-last=Gill | editor1-first=Frank | editor1-link=Frank Gill (ornithologist) | editor2-last=Donsker | editor2-first=David | editor3-last=Rasmussen | editor3-first=Pamela | editor3-link=Pamela Rasmussen | date=July 2021 | title=Noddies, gulls, terns, skimmers, skuas, auks | work=IOC World Bird List Version 11.2 | url=https://www.worldbirdnames.org/bow/gulls/ | publisher=International Ornithologists' Union | accessdate=16 August 2021 }}</ref> 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''.<ref name=Linnaeus/> Razorbills and great auks are part of the [[Tribe (biology)|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'').<ref name=Friesen/>

There are two subspecies of razorbill accepted by the IOC:<ref name=ioc/>
{| class="wikitable "
|-
! Image !! Subspecies !! Distribution
|-
|[[File:Razorbills.jpg|120px]]<br>Stora Karlsö, Gotland, Sweden||''Alca torda torda'' {{au|[[Carl Linnaeus|Linnaeus]] 1758}} || the [[Baltic Sea|Baltic]] and [[White Sea]]s, [[Norway]], [[Bear Island (Norway)|Bear Island]], [[Greenland]], and eastern [[North America]]. 
|-
|[[File:Razorbills and Puffins.jpg|120px]]<br>Látrabjarg, Iceland (with [[Atlantic puffin]]s to the right)||''Alca torda islandica'' {{au| [[Christian Ludwig Brehm|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.<ref name = HBW/> A third subspecies ''Alca torda pica'' Linnaeus, 1766 (originally described as a species ''Alca pica'' from the Arctic,<ref>{{cite book | last=Linnaeus | first= C. | author-link= Carl Linnaeus | year=1766 | title= Systema Naturæ per regna tria naturae, secundum classes, ordines, genera, species, cum characteribus, differentiis, synonymis, locis, Volume 1| volume= 1 | edition=12th | page=210 | publisher=Holmiae:Laurentii Salvii  | language = Latin | url= https://www.biodiversitylibrary.org/page/42946406 }}</ref> and reduced to subspecies by [[Finn Salomonsen|Salomonsen]] in 1944<ref>{{cite journal |last1=Storer |first1=Robert W. |title=Publications Reviewed |journal=Condor |date=1947 |volume=49 |page=91 |doi=10.2307/1364125 |jstor=1364125 |url=https://sora.unm.edu/sites/default/files/journals/condor/v049n02/p0091-p0091.pdf |access-date=11 September 2024}}</ref>), is no longer accepted because the distinguishing characteristic, an additional furrow in the upper mandible, is now known to be age-related.<ref name = HBW/>

==Description==
[[File:Razorbill (Alca torda) pair.jpg|thumb|Courting on [[Skomer Island]]]]
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.<ref name=LPZRazorbill/> 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 {{cvt|505|to|890|g|oz|frac=4}}.<ref name=Conder/> The female and male adults are very much alike, having only small differences such as wing length. It is 37–39&nbsp;cm in body length, the wing length of adult males ranges from {{cvt|201|–|216|mm|in|frac=16}} while that of females ranges from {{cvt|201|to|213|mm|in|frac=16}}.<ref name=Gaston/> 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 [[Bird colony|colonial]] breeder and only comes to land to breed. The annual survival rate of the razorbill is between 89 and 95%.<ref name=NRC/> 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.<ref name=McCarthy/>

== 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.<ref name=Chapdelaine2001/> Approximately half of the breeding pairs occur in Iceland. Razorbills thrive at water surface temperatures below {{cvt|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 Ocean|Atlantic]] coasts, in eastern [[North America]] as far south as [[Maine]], and in western [[Europe]] from northwestern [[Russia]] to northern [[France]].  North American birds [[Bird migration|migrate]] offshore and south, ranging from the [[Labrador Sea]] south to the [[Grand Banks]] of [[Newfoundland (island)|Newfoundland]] to [[New England]].  Eurasian birds also winter at sea, with multiple populations aggregating in the North Sea<ref name="Buckingham et al. 2022">{{cite journal |last1=Buckingham |first1=Lila |last2=Bogdanova |first2=Maria I. |last3=Green |first3=Jonathan A. |last4=Dunn |first4=Ruth E. |last5=Wanless |first5=Sarah |last6=Bennett |first6=Sophie |last7=Bevan |first7=Richard M. |last8=Call |first8=Andrew |last9=Canham |first9=Michael |last10=Corse |first10=Colin J. |last11=Harris |first11=Michael P. |last12=Heward |first12=Christopher J. |last13=Jardine |first13=David C. |last14=Lennon |first14=Jim |last15=Parnaby |first15=David |last16=Redfern |first16=Chris P. F. |last17=Scott |first17=Liz |last18=Swann |first18=Robert L. |last19=Ward |first19=Robin M. |last20=Weston |first20=Ewan D. |last21=Furness |first21=Robert W. |last22=Daunt |first22=Francis |title=Interspecific variation in non-breeding aggregation: a multi-colony tracking study of two sympatric seabirds |journal=Marine Ecology Progress Series |date=17 February 2022 |volume=684 |pages=181–197 |doi=10.3354/meps13960 |bibcode=2022MEPS..684..181B |s2cid=244752949 |language=en |issn=0171-8630|doi-access=free }}</ref> and some moving south as far as the western [[Mediterranean]]. Approximately 60 to 70% of the entire razorbill population breeds in [[Iceland]].<ref name=BNA/>

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.<ref name=lilliendahl2003/>
* [[Runde]], Norway (62°24' N) - 3,000 pairs.
* [[St Kilda, Scotland|St Kilda]], Scotland (57°49' N).
* [[Stora Karlsö]], Gotland, Sweden (57°17' N), the type locality and the largest colony in the Baltic Sea, with 12,000 pairs in 2014–2015.<ref>{{cite web |title=Fåglarna |url=https://storakarlso.se/faglarna/ |website=Stora Karlsö |access-date=11 September 2024 |language=Swedish }}</ref>
* [[Farne Islands]], Northumberland, UK (55°38' N) - 523 pairs in 2022, breeding season May to mid-July.<ref>{{cite book |editor1-last=Mould |editor1-first=Andy |title=Birds in Northumbria 2022 |date=2023 |publisher=Northumberland and Tyneside Bird Club |location=Newcastle upon Tyne |isbn=978-1-9993398-5-2 |page=110}}</ref>
* [[Bempton Cliffs]], [[East Riding of Yorkshire]], UK (54°14’ N) - 30,673 pairs in 2022, pairs from March to mid-July.<ref>{{cite book |last1=Clarkson |first1=K. |last2=Aitken |first2=D. |last3=Cope |first3=R. |last4=O'Hara |first4=D. |title=Flamborough & Filey Coast SPA: 2022 seabird colony count and population trends |date=2023 |page=30 |url=https://yorkshiremarinenaturepartnership.org.uk/wp-content/uploads/2022/11/Flamborough-and-Filey-Coast-SPA-seabird-colony-count-2022.pdf |access-date=11 September 2024}}</ref>
* [[Skomer Island]], Pembrokeshire, Wales.
* [[Heligoland]], Germany (54°10' N) - a few pairs only.
* [[Gannet Islands Ecological Reserve|Gannet Islands]], Canada (53°58' N) - 9,800 pairs.<ref name=Chapdelaine2001/>
* [[Funk Island]], Canada (49°45' N).
* [[Île Rouzic]], Brittany, France (48°54' N) - the southernmost limit in Europe; 600 pairs in 1960 but declining to just 30 pairs by 2006.<ref>{{cite web |title=La Liste rouge des espèces menacées en France |url=http://www.uicn.fr/IMG/pdf/Liste_rouge_France_Oiseaux_de_metropole.pdf |publisher=UICN Comité Français |access-date=11 September 2024 |archive-url=https://web.archive.org/web/20150226071157/http://www.uicn.fr/IMG/pdf/Liste_rouge_France_Oiseaux_de_metropole.pdf |archive-date=2015-02-26 |page=6 |language=French}}</ref>
* [[Baccalieu Island]], Canada (48°07' N).
* [[Witless Bay Ecological Reserve|Witless Bay]], Canada (47°13' N).
* [[Cape St. Mary's Ecological Reserve|Cape St. Mary's]], Canada (46°49' N).

== Behaviour ==
[[File:Razorbill (Alca torda) taking off.jpg|thumb|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,<ref>{{cite web|url= https://www.audubon.org/field-guide/bird/razorbill | title=Razorbill=29 December 2022|work=audubon}}</ref> 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.<ref name=wagner/> Once a male is chosen, the pair will stay together for life.

=== Reproduction ===
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.<ref name=Conder/> [[Courtship display]]s 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.<ref name=Conder/> The pair will mate up to 80 times in a 30-day period to ensure fertilisation.<ref name=Wagner1992/> Females will sometimes encourage other males to engage in copulation to guarantee successful fecundity.<ref name=wagner/>

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 ===
[[File:Banded Razorbill chick.jpg|thumb|upright|Banded chick on [[Gannet Islands Ecological Reserve|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 {{cvt|10|cm|in|0}} 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.<ref name=Plumb/>

The mating pair will often reuse the same site every year.<ref name=Harris/><ref name=Lavers2007/> 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.<ref name=Williams/> Nest under a boulder, rarely on an exposed ledge, may use Puffin or rabbit burrow.<ref name=":0">{{Cite book|last=Snow|first=D. W.|title=The Birds of the Western Palearctic|publisher=Oxford University Press|year=1994|isbn=0-19-850187-0}}</ref> Although gregarious in breeding colonies, nests are not contiguous, but some metres apart, resulting in less aggression than in Guillemot colonies.<ref name=":0" />

=== Incubation and hatching ===
[[File:Alca torda MHNT Île Rouzic.jpg|thumb|upright|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. [[Avian incubation|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]].<ref name=Ralph/> 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.<ref>{{Cite journal|last1=Dunn|first1=Ruth E.|last2=Wanless|first2=Sarah|last3=Green|first3=Jonathan A.|last4=Harris|first4=Michael P.|last5=Daunt|first5=Francis|date=2019|title=Effects of body size, sex, parental care and moult strategies on auk diving behaviour outside the breeding season|journal=Journal of Avian Biology|language=en|volume=50|issue=7|doi=10.1111/jav.02012|s2cid=164436494|issn=1600-048X|doi-access=free}}</ref>

=== 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 {{cvt|25|m|ft|round=5}} but they have the ability to dive up to {{cvt|120|m|ft|round=5}} below the surface.<ref name=Piatt/> 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.<ref name=Thaxter/>

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.<ref name=Conder/> Females will generally feed their chicks more frequently than males.<ref name=Thaxter/> They may fly more than {{cvt|100|km|mi|-1}} out to sea to feed when during egg incubation, but when provisioning the young, they forage closer to the nesting grounds, some {{cvt|12|km|mi|frac=2}} away, and often in shallower water.<ref name=lilliendahl2003/>

=== 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 [[capelin]], [[sand lance|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.<ref name=Lavers2007/>

== Predators ==
The adult razorbill has several predators which include [[great black-backed gull]]s, [[peregrine falcons]], [[raven]]s, [[crows]], and [[western jackdaw|jackdaws]]. The general predators of their eggs are [[gulls]] and [[raven]]s. The best chance for adult razorbill to avoid predation is by diving. [[Arctic fox]]es and [[polar bears]] can also predate significant numbers of adults, eggs, and chicks in some years in the north of the species' range.<ref name=Lavers2009/>

Razorbill eggs were collected until the late 1920s in [[Scotland]]'s remote [[St Kilda, Scotland|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.<ref>The Daily Mail April 18 1930: article by Susan Rachel Ferguson</ref>

== Conservation and management ==
[[File:BirdsMSI.jpg|thumb|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.<ref name=Conder/> 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''.<ref name=Fuller/> A number of fossil forms have been found:

* ''Alca'' "''antiqua''" (Late Miocene/Early Pliocene of Lee Creek Mine, US){{citation needed|date=January 2008 |reason=species name invalid, preoccupied by [[Ancient murrelet|''Synthliboramphus antiquus'']] (ancient murrelet) which was originally described in ''Alca''}}
* ''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]].<ref name=Bedard/>

== References ==
{{Reflist|refs=

<ref name=LPZRazorbill>{{cite web |url=http://www.lpzoo.org/animals/factsheet/razorbill |title=Razorbill Fact Sheet |publisher=Lincoln Park Zoo |archive-url=https://web.archive.org/web/20110929033013/http://www.lpzoo.org/animals/factsheet/razorbill |archive-date=29 September 2011 |url-status=dead}}</ref>

<ref name=Conder>{{cite journal |last=Conder |first=P.J. |title=On the courtship and social displays of three species of auk |journal=British Birds |volume=43 |pages=65–69 |year=1950 }}</ref>

<ref name=Gaston>{{cite book |last1=Gaston |first1=Anthony J. |last2=Jones |first2=Ian L. |title=The Auks: Alcidae |series=Bird Families of the World |publisher=Oxford University Press |location=New York |pages=126–132 |year=1998 |isbn=978-0198540328}}</ref>

<ref name=NRC>{{cite journal |title= Annual survival of North American Razorbills (''Alca torda'') varies with ocean climate indices |last1=Lavers |first1=J.L. |last2=Jones |first2=I.L. |last3=Diamond |first3=A.W. |last4=Robertson |first4=G.J. |year=2008 |doi=10.1139/Z07-113 |journal=Canadian Journal of Zoology |pages=51–61 |volume=86 |issue=1 |publisher=NRC Research Press |bibcode=2008CaJZ...86...51L }}</ref>

<ref name=McCarthy>{{cite news |last=McCarthy |first=Michael |date=10 July 2008 |title=Seabird Born in Summer of Love Still Breeding in Wales |url=https://www.independent.co.uk/environment/nature/seabird-born-in-summer-of-love-still-breeding-in-wales-863919.html |newspaper=The Independent |location=London |access-date=10 July 2008 }}</ref>

<ref name=Friesen>{{cite journal |last1=Friesen |first1=V.L. |last2=Baker |first2=A.J. |last3=Piatt |first3=J.F. |title=Phylogenetic relationships within the Alcidae (Charadriiformes: Aves) inferred using total molecular evidence |journal=Molecular Biology and Evolution |volume=13 |pages=359–367 |year=1996 |issue=2 |doi=10.1093/oxfordjournals.molbev.a025595 |pmid=8587501|doi-access=free }}</ref>

<ref name=BNA>{{Cite book |last1=Lavers |first1=J.L. |last2=Hipfner |first2=M.J. |last3=Chapdelaine |first3=G.C. |title=The Birds of North America |publisher=The Birds of North America, Inc. |volume=16 |location=Philadelphia, PA |year=2009 |issue=635}}</ref>

<ref name=wagner>{{cite journal |last=Wagner |first=R.H. |title=Evidence that female Razorbills control extra pair copulations |journal=Behaviour |publisher=BRILL |volume=118 |issue=3/4 |year=1991 |pages=157–169 |jstor=4534962 |doi=10.1163/156853991X00265}}</ref>

<ref name=Chapdelaine2001>{{cite report |last1=Chapdelaine |first1=G. |first2=A.W. |last2=Diamond |first3=R.D. |last3=Elliot |first4=G.J. |last4=Robertson |year=2001 |title=Status and population trends of the Razorbill in eastern North America |publisher=Canadian Wildlife Service |series=Occasional Paper |number=105 |url=http://publications.gc.ca/pub?id=392816&sl=0}}</ref>

<ref name=Wagner1992>{{cite journal |last=Wagner |first=R.H. |title=Confidence of paternity and parental effort in razorbills |journal=The Auk |volume=109 |number=3 |pages=556–562 |year=1992 |publisher=American Ornithologists' Union |jstor=4088369}}</ref>

<ref name=Plumb>{{cite journal |last=Plumb |first=W.J. |title=Observations on the breeding biology of the Razorbill |journal=British Birds |volume=58 |number=11 |year=1965 |pages=449–456 |url=http://www.britishbirds.co.uk/wp-content/uploads/article_files/V58/V58_N11/V58_N11_P449_456_A085.pdf |access-date=14 September 2014 |archive-date=16 July 2015 |archive-url=https://web.archive.org/web/20150716212545/http://www.britishbirds.co.uk/wp-content/uploads/article_files/V58/V58_N11/V58_N11_P449_456_A085.pdf |url-status=dead }}</ref>

<ref name=Harris>{{cite journal |last1=Harris |first1=M.P. |last2=Wanless |first2=S. |title=The breeding biology of Razorbills Alca torda on the Isle of May |journal=Bird Study |volume=36 |number=2 |pages=105–114 |year=1989 |doi=10.1080/00063658909477012|bibcode=1989BirdS..36..105H }}</ref>

<ref name=Lavers2007>{{cite journal |last1=Lavers |first1=J.L. |last2=Jones |first2=I.L. |title=Factors affecting rates of intraspecific kleptoparasitism and breeding success of the Razorbill at the Gannet Islands, Labrador |journal=Marine Ornithology |volume=35 |number=1 |pages=1–7 |year=2007 |doi=10.5038/2074-1235.35.1.715 |url=http://www.marineornithology.org/PDF/35_1/35_1_1-7.pdf}}</ref>

<ref name=Williams>{{cite journal |last=Williams |first=A.J. |title=Laying and nest-building behavior in the larger auks (Aves, Alcidae) |journal=Astarte |volume=4 |pages=61–67 |year=1971}}</ref>

<ref name=Ralph>{{cite report |editor1-first=C. John |editor1-last=Ralph |editor2-first=George L. |editor2-last=Hunt Jr. |editor3-first=Martin G. |editor3-last=Raphael |editor4-first=John F. |editor4-last=Piatt |title=Ecology and Conservation of the Marbled Murrelet |publisher=USDA Forest Service |volume=PSW-152 |year=1995 |location=Albany, California |url=http://www.fs.fed.us/psw/publications/documents/gtr-152/}}</ref>

<ref name=Piatt>{{cite journal |last1=Piatt |first1=J.F. |last2=Nettleship |first2=D.N. |title=Diving depths of four alcids |journal=The Auk |volume=102 |issue=2 |pages=293–297 |year=1985 |doi=10.2307/4086771|jstor=4086771 }}</ref>

<ref name=Thaxter>{{cite journal |last1=Thaxter |first1=Chris B. |last2=Daunt |first2=Francis |last3=Hamer |first3=Keith C. |last4=Watanuki |first4=Yutaka |last5=Harris |first5=Mike P. |last6=Grémillet |first6=David |last7=Peters |first7=Gerrit |last8=Wanless |first8=Sarah |title=Sex-specific food provisioning in a monomorphic seabird, the common guillemot ''Uria aalge'': nest defence, foraging efficiency or parental effort? |journal=Journal of Avian Biology |volume=40 |issue=1 |pages=75–84 |year=2009 |doi=10.1111/j.1600-048x.2008.04507.x}}</ref>

<ref name=lilliendahl2003>{{cite journal |last1=Lilliendahl |first1=K. |last2=Solmundsson |first2=J. |last3=Gudmundsson |first3=G.A. |last4=Taylor |first4=L. |year=2003 |title=Can surveillance radar be used to monitor the foraging distribution of colonially breeding alcids? |language=en, es |journal=[[Condor (journal)|Condor]] |volume=105 |issue=1 |pages=145–150 |doi=10.1650/0010-5422(2003)105[145:CSRBUT]2.0.CO;2 |s2cid=29136400 |doi-access=free }}</ref>

<ref name=Lavers2009>{{cite journal |last1=Lavers |first1=J.L. |last2=Jones |first2=I.L. |last3=Robertson |first3=G.J. |last4=Diamond |first4=A.W. |title=Contrasting population trends at two Razorbill colonies in Atlantic Canada: additive effects of fox predation and hunting mortality? |journal=Avian Conservation and Ecology |volume=4 |issue=2 |pages=3–17 |year=2009 |doi=10.5751/ACE-00322-040203 |doi-access=free }}</ref>

<ref name=Fuller>{{cite book |last=Fuller |first=Errol |title=The Great Auk |publisher=Privately Published |location=Southborough, Kent, UK |year=1999 |edition=Illustrated |page=401 |isbn=0-9533553-0-6}}</ref>

<ref name=Bedard>{{cite book |last=Bédard |first=J. |year=1985 |chapter=Evolution and characteristics of the Atlantic Alcidae |editor1-last=Nettleship |editor1-first=David N. |editor2-last=Birkhead |editor2-first=Tim R. |title=The Atlantic Alcidae |pages=6–19 |publisher=Academic Press |location=London |isbn=0-12-515671-5}}</ref>
}}

== External links ==
{{Commons category|Alca torda}}
{{Wikispecies|Alca torda}}
* {{EBirdSpecies|razorb|Razorbill}}
* {{VIREO|Razorbill}}
* {{IUCN_Map|22694852/228697220|Alca torda}}
* {{Xeno-canto species|Alca|torda|Razorbill}}

{{Taxonbar|from=Q27102}}
{{Authority control}}

[[Category:Alcini]]
[[Category:Atlantic auks]]
[[Category:Birds of Europe]]
[[Category:Birds of Greenland]]
[[Category:Birds of Iceland]]
[[Category:Birds of Scandinavia]]
[[Category:Birds described in 1758]]
[[Category:Taxa named by Carl Linnaeus]]