Auks (family Alcidae) are diving seabirds, including murres, puffins, guillemots, and auklets. These marine birds share black-and-white plumage and an upright posture, often leading to comparisons with penguins, though they are not closely related. Their compact bodies and short, narrow wings are adapted for “flying” underwater, allowing them to pursue fish and invertebrates deep beneath the surface. Adaptations like webbed feet and legs set far back on the body make them agile swimmers but somewhat clumsy on land.
Cold Water Specialists: The Northern Hemisphere Range
Auks are limited to the Northern Hemisphere, inhabiting the cooler waters of the world’s oceans. Their distribution is concentrated in the boreal, sub-Arctic, and Arctic zones, depending on cold, nutrient-rich marine ecosystems. Cold temperatures are important because the primary hunting method of auks—pursuit diving—is most efficient where their prey’s swimming speed is lower.
The need for cold water restricts their range, making them indicators of healthy high-latitude marine environments. The two major ocean basins that serve as the home range for the family are the North Pacific and the North Atlantic. While a few species can survive in more southern areas, such as Baja California, they rely on localized cold-water upwellings to sustain their food supply.
The Dual Existence: Breeding Colonies and Pelagic Life
The life of an auk is defined by two habitats. For the majority of their adult lives, auks are pelagic, spending time on the open ocean, often hundreds of miles from any coastline. Auks dedicate this offshore existence to foraging, diving to impressive depths, sometimes over 300 feet, to hunt schooling fish and zooplankton.
Auks come ashore only for the breeding season. Their onshore locations are typically dense colonies established on steep coastal cliffs, rocky islands, and headlands. This rugged terrain provides natural protection from land predators, allowing the birds to nest and raise their single chick safely.
Some species, like puffins and certain auklets, will dig burrows on grassy slopes or among boulders, while others, such as murres, lay their eggs directly on open cliff ledges. This split between the open, food-rich sea and the safe, predator-free land highlights their life cycle. The ability to find both a secure nesting site and productive foraging waters determines the location of their colonies.
Species-Specific Habitats: North Pacific vs. North Atlantic
Different species partition the northern habitat, often segregating by ocean basin. The North Pacific is home to the vast majority of species, hosting around 19 to 20 species, while the North Atlantic currently supports only six species. This difference is thought to be a result of past extinctions in the Atlantic, where the fossil record shows greater historical diversity.
Species like the Common Murre (or Common Guillemot in Europe) are widespread, with breeding populations in both the North Pacific and North Atlantic. However, many auks are specific to one ocean, such as the Horned Puffin, which breeds in the North Pacific from Alaska down to British Columbia. Conversely, the Razorbill is strictly a North Atlantic breeder, found from eastern Canada to Scandinavia. The North Pacific also contains the entire genus of Auklets, including the Least and Crested Auklets, which thrive in the Bering Sea and surrounding waters.
Seasonal Migration Patterns
Auks follow a predictable seasonal cycle of movement. After the summer breeding season ends, auks leave their nesting colonies and disperse across the open ocean. This movement is primarily driven by the need to follow shifting food resources and to avoid the formation of sea ice in the high Arctic.
While some species remain relatively close to their breeding grounds, many undertake short-distance coastal migrations or move substantial distances over the continental shelf. For example, the Little Auk (Dovekie) will move from its high Arctic breeding sites in Greenland and Svalbard to wintering areas further south, such as off Newfoundland. These movements are not typically trans-oceanic; instead, they represent a shift to lower latitudes or to offshore areas where food remains accessible throughout the winter.