Murres are slimmer-billed. Breeds along Atlantic coast on coastal islands, rocky cliffs. Gather in rafts near islands or cliffs where they will nest, to court. Often seen carrying many fish in its bill back to nest site. Winters in the open Atlantic, farther out and in deeper waters than Murres and Razorbills.
Mating system is monogamous.
Pair engage bills, then bill and neck. Crevice often in cliff or among rocks. Usually lined with grass, leaves, feathers, occasionally unlined. Male builds nest. Incubation takes 39-45 days.