In winter the Polar Ocean is largely barren. In spring, however, the sunlight produces a bloom of unicellular algae near the surface, which provides food for the microscopic animal life that forms the basis of the oceanic food chain. In spring, shoals of pelagic fish come northwards through the northern island barrier to feed on the zooplankton, bringing with them countless numbers of seabirds.
The first bird species to arrive is the flightless auk, a totally aquatic creature with paddle-like wings. In this respect they resemble the penguins, which were so successful in the Southern Hemisphere in earlier times. Except during winter the flightless auks rarely come ashore or climb onto the ice, where they are quite defenseless. Pregnant females retain their eggs until they are almost ready to hatch and lay them in the open water.The flightless auks first evolved at the northernmost tip of the Northern Continent and, as they became established, spread both east and west, forming a chain of subspecies in a ring around the Polar Ocean. Throughout most of the ring each subspecies is able to breed with the neighboring ones, but where the ends of the chain overlap the differences are so great that no interbreeding is possible and these populations must be regarded as separate species.
Flightless auks are often preyed on by pytherons.