This stocky, robust, crow-sized seabird is widely distributed through boreal and low-arctic Atlantic waters; the bulk of the world population breeds in Iceland. From there, colonies stretch east through northern Europe and northwestern Russia. In the northwest Atlantic, Razorbills breed mainly in small colonies, few supporting more than 1,000 breeding pairs, scattered from northwestern Greenland and Hudson Strait, south through the Atlantic provinces of Canada to Maine. The center of the North American breeding distribution is in low-arctic waters of southern Labrador and the lower North Shore of the Gulf of St. Lawrence. With only about 300 pairs nesting in Maine, the Razorbill is among the least numerous of all breeding seabirds in US waters. Most Razorbills from North American colonies overwinter south of their breeding range in ice-free, coastal waters, with largest numbers frequenting shoal areas in the outer Bay of Fundy and Gulf of Maine. The species occurs regularly in winter south to Long Island, NY, and New Jersey, and rarely to Virginia, with casual records to Florida.
Given the Razorbill's remote distribution and relatively small numbers (about 38,000 breeding pairs) in North America, it is not surprising that its biology is poorly known at most breeding sites. Individuals breed on rocky islands and steep, mainland cliffs. Most use nest sites that are partly or wholly enclosed, often in crevices among boulders.
The life-history strategy of this species is typical of marine birds: socially monogamous, with strong mate and nest-site fidelity; an approximately 90% annual adult-survival rate, with deferred breeding until 4 or 5 years of age; and a single-egg clutch. Timing of breeding varies depending on oceanographic conditions; egg-laying begins 2-6 weeks earlier in boreal than in low-arctic waters. Incubation averages 35 days, and the male parent accompanies the chick to sea after about 18-20 days at the nest site. At nest departure, the chick weighs only 25-30% of adult mass and has not yet begun to grow the large feathers of the wings and tail. This unusual "intermediate" developmental strategy is otherwise employed only by Common (Uria aalge) and Thick-billed murres (U. lomvia), the Razorbill's closest extant relatives. While ecologically similar, Razorbills and murres differ in a number of important respects, such as their nesting habits, and these differences provide fertile ground for comparative studies.
Wing-propelled divers that feed mainly on schooling fish, Razorbills occasionally descend to ocean depths greater than 100 meters. In North America, important prey species include capelin (Mallotus villosus), herring (Clupea harengus), and sandlance (Ammodytes spp.), varying with location and season. Crustaceans and polychaetes are also important in adult diets, the former perhaps especially in winter. Nestlings receive about 2-4 feedings daily, each consisting of 1-8 fish, which the adult birds carry to the nest site held crosswise in the bill. Razorbills are strong and rapid fliers, yet remarkably agile in flight compared to other large Alcidae. Foxes, gulls, and ravens are important predators of Razorbill eggs and chicks.
Heavily persecuted by humans for eggs, meat, and feathers, Razorbill populations were greatly reduced, even locally extirpated, across much of their northwest Atlantic breeding range by early in the twentieth century. Although largely protected since 1917 in the northwest Atlantic, the species was slow to recover as direct harvesting and incidental killing continued in key regions. With stricter enforcement of regulations, however, and improved education programs, Razorbill populations have increased dramatically in North America over the last 20 years-an encouraging sign, although the long-term welfare of the species remains a concern in the face of grave, human threats to northwest-Atlantic ecosystems.