Editing Razorbill (section)

== 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/>