Seabirds are important and conspicuous upper-trophic marine predators, consuming a variety of larval, juvenile and adult fish (age-0 pollock, myctophids), zooplankton (euphausiids, copepods), and squid.  In the North Pacific Ocean, seabirds exhibit a broad range of life histories, from the deep-diving murres to the surface-feeding albatrosses. They occupy a variety of habitats, with different species assemblages inhabiting distinct tropical and sub-arctic ocean regions. The broad range of seabird life-styles is illustrated by their large range in body size, from the small-sized storm-petrels (45 g in weight, with a wing span of 21 cm) to the large albatrosses (3,400 g in weight, with a wing span and of over 180 cm).

Albatross over the Bering Sea .

An estimated 20 million seabirds breed in the Bering Sea (U.S. Fish and Wildlife Service Beringian Seabird Colony Catalog), and another 20-30 million join in an annual spring/summer migration from distant locations to take advantage of the high productivity of this area.  Some travel from as far away as Tasmania in the southern hemisphere. Other seabird species migrate through the Bering Sea on their way to breeding grounds farther north in the Arctic (see Conservation of Arctic Flora and Fauna).  Visit these links to learn more about Alaskan seabird populations (Alaska Maritime National Wildlife Refuge Birds area) and their ecology (U.S. Geological Survey Seabirds site).

Murres on an ice floe .

Even though seabirds are numerous in the Bering Sea, little is known about how they use the ice-edge environment.  Do some spring visitor species feed along the ice edge to take advantage of local prey concentrations?  Do some migrating species concentrate at the ice edge waiting for it to retreat northwards? Are some parts of the ice edge, like the leads (large “veins” or “branches” of open water that cut into the sea ice and extend many kilometers), more important for foraging and migrating seabirds?

Storm petrel .

Where seabird studies have been conducted in the Arctic and the Antarctic, researchers have found that many species concentrate in the marginal ice zone (the transition between open and ice-covered waters) to forage and to wait for the sea ice to open up so they can continue their seasonal migration.  We expect to find major concentrations of seabirds along the Bering Sea ice-edge habitat, but what species will be present, where along the ice edge they will aggregate, and what prey will be available to them remains a mystery.  To answer these questions, we will count birds from the bridge of the research vessel while we sail along transects running from the open water towards the ice edge.  Stay tuned to find out what stories the birds have to tell.

If you have any questions, you can e-mail David Hyrenbach, the scientist who wrote this article, but don't forget that he will be with us at sea for many weeks. If you have a seabird question during the cruise, e-mail the ship using our "Ask a Scientist" page.