The Atlantic Puffin is the only puffin within its range. Its huge, colorful bill is diagnostic. Immatures can look vaguely similar to Razorbills but have a grayish face and lack the white secondary bar.
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.