An alternate form, or the bridled morph, only occurs in a population in the North Atlantic. It has an eye ring with a line extending toward the back of its head in addition to the regular adult plumage. Chicks are downy when first hatched. They are blackish brown on top and white underneath. When they are first hatched they weigh 55-95 grams.
Juveniles are similar to adults except for their smaller size and darker heads.
The common murre is mainly piscivorous. They are surface divers that can remain submerged for up to one minute at a time. They often dive to a depth of 100 feet but have been recorded to reach a depth of 550 feet. They use their strong wings to fly underwater. Adults consume between 20g and 32g of food everyday.