Razor-billed auk, Lesser auk
The razorbill (Alca torda) is a 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. In 1918, the razorbill was protected in the United States by the Migratory Bird Treaty Act. Presently, this species faces several major threats but luckily its population appears to be increasing or stable at the present.
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. 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. 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. The female and male adults are very much alike, having only small differences such as wing length. 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.
Razorbills are found across the sub-arctic and boreal waters of the North Atlantic. They thrive at water surface temperatures below 15 °C and, unlike other auks, they often move into larger estuaries with lower salinity levels to feed. 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 and some moving south as far as the western Mediterranean. Approximately 60 to 70% of the entire razorbill population breeds in Iceland.
Razorbills are very social birds that nest in colonies and often fly in flocks. They are often seen with the two larger auks, Thick-billed murres and Common murres. During the colder months, razorbills leave land and spend the entire winter in the waters of the Atlantic Ocean. They are agile birds, which are capable of both flight and diving. 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. 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. 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 (60 mi) out to sea to feed during egg incubation, but when provisioning the young, they forage closer to the nesting grounds, some 12 km (7.5 mi) away, and often in shallower water.
Razorbills are carnivores (piscivores). They feed on mid-water schooling fish such as capelin, sand lance, juvenile cod, sprats, and herring. They may also eat crustaceans and polychaetes.
Razorbills are monogamous breeders. 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. 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. As pairs grow older they will occasionally skip a year of breeding. During breeding, both males and females protect their nest site from neighboring pairs. Once the pre-laying period begins, males will constantly guard their mates by knocking other males away with their bills. Throughout the pre-laying period, razorbills socialize in large numbers. Large groups dive and swim together in circles repeatedly and all rise up to the surface, heads first and bills open; large groups may also swim in a line weaving across each other in the same direction. Nest site choice is very important for razorbills to ensure the protection of their young from predators. They don’t’ nest 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. The mating pair will often reuse the same site every year. 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. Females lay a single egg per year, usually from late April to May. The egg is an ovoid-pyramidal shape, cream color with dark brown blotches. Incubation starts generally 48 hours after laying the egg. Females and males take turns incubating the egg for 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. 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 the sea. During this time, the male parent will dive more than the female parent. Young razorbills become reproductively mature and start to breed at 3-5 years of age.
Today these birds suffer from 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.
According to the IUCN Red List, the total population size of the razorbill is 1,257,000-2,490,000 individuals or 838,000-1,660,000 mature individuals. The European population is estimated at 519,000-1,070,000 mature individuals. Currently, this species is classified as Least Concern (LC) on the IUCN Red List, and its numbers today are increasing.
