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.