The alcids are sometimes referred to as the “penguins of the north” because of their similar body designs. All of the twenty or so species of alcids share a few basic characteristics: stout, streamlined bodies; short, narrow wings; thick, waterproof plumage; short tails; and feet set well back on the body. Most species have a crisp, black and white plumage pattern, reminiscent of the flightless birds of the Southern Hemisphere. Only one species of alcid, the great auk, was truly flightless like penguins. Bones of this huge bird have been found in archaeological sites of Cape Cod and they may have visited Stellwagen Bank at some point during their migrations. Little can be known of their habits here as they were hunted out of existence over 300 years ago.
More than any other group of birds on Stellwagen, the alcids are built for a marine life. Powered along by strong chest muscles, alcids are swift fliers through the air and the water. With half opened wings, alcids can swim down to great depths to hunt fish, squid or large plankton. Each species sharing a particular habitat tends to specialize on different prey and their differing body designs and habits reflect this. Most species breed on islands further to the north, heading south and offshore for the winter. The nesting season is brief and half-grown chicks may be accompanied at sea by one or both parents for a few weeks after fledging. The same pairs may use the same nest sites year after year and individuals are long lived.
Sightings of alcids on Stellwagen coincide with their southerly migrations and vary greatly from year to year. The razorbill may be the most commonly seen alcid on the Bank while sightings of the other species are strongly dependent upon changes in food supply or storms.
Black Guillemot, Cepphus grylle, are found throughout the Northern Hemisphere, breeding on small rocky islands and hunting offshore. With a 60cm (2 foot) wingspan, black white wing patches (in summer plumage) and bright red feet and throat lining, guillemots are very distinctive. They tend to be wary, diving out of view at the approach of boats. Small flocks may be seen flying low over the water with their plump bodies creating a distinct “pot-bellied” appearance. Sitting on the water, their short tails often point straight up and they may dip their bills regularly. Their plumage molts to white and grayish-brown in winter. Hunting in the shallows of bays and banks, guillemots specialize on small fish hiding among rock and kelp reefs.
Razorbill, Alca torda, are large, heavy alcids (45cm or 17 inches) built for deep diving and pursuit. Like many marine animals, they are dark (black) above and light (white) below, perhaps as camouflage against the light of the surface or dark of the depths. Their massive head and bill are distinctive. At sea, they are often seen bobbing on the waves, their longish tail and bill angled skyward. Nesting on a few small islands within the Gulf of Maine (with larger colonies further north) pairs are strongly bonded to a nest site. Outside of the nesting season, pairs separate to forage at sea. Individuals can live beyond twenty years. On Stellwagen, razorbills may be the most commonly seen alcid from November through early spring. They have been seen with many sand lance held crosswise in the bill.
Atlantic puffin, Fratercula arctica, are probably the most popular alcid in the North Atlantic; their bright bills and bold plumage are unforgettable. During severe, offshore storms, flocks may be driven close to the coast but sightings of these birds on Stellwagen are sporadic at best. Using their stubby wings, puffins pursuit dive for bait fish, such as herring and sand lance. Their deep, laterally compressed bills allow parents to carry a mouthful of fish back to their chicks, hidden in burrows on quiet islands. Colonies have been rebuilding their numbers after years of harvesting adults and eggs for food and the introduction of rats, cats and dogs to their breeding islands.
Dovekie, Alle alle, are the smallest alcid in the Atlantic (20cm or 8 inches long). Their short necks and plump, black and white bodies are distinctive. In flight their wing beats are a blur of speed. On the water they tend to sit low and may form massive flocks. For takeoff, dovekies need height or wind; birds stranded on land may not be able to take flight. Dovekies are quite rare on Stellwagen. Their winter range rarely extends this far south or this close to shore. Autumn storms may blow scattered flocks inshore or even inland.
Thick-billed murre, Uria lomvia, and common murre, Uria aalge, are biggish alcids of similar appearance. Their long, thick necks support large heads and long bills. At sea, the species can be difficult to distinguish but, the thick-billed murre has a white line running the length of the upper bill. During the breeding season, both species may be found nesting together on sea cliffs. Their eggs are incubated on the slimmest of ledges, their long pointed design prevents dangerous rolling. Individual eggs are variously marked so that returning adults can find them amidst the throng of the colony. At sea they are like other alcids but, their dives carry them exceptionally deep: they have been found entangled in fishing gear at 76m (250 feet). Sightings of murres on Stellwagen vary from year to year and may be dependent upon prey and weather.