• The common guillemot can live almost 43 years. Scientists have encountered individuals reaching this age, and it is a record for birds of this species.
• Common guillemot chicks fall from a height of up to 40 m onto a rocky beach, but do not break due to a layer of fat formed in previous weeks. Fat layers protect them when they are not yet able to fly.

Common guillemots typically live for ten to twenty years, although the maximum recorded lifespan is forty-two years and ten months, with a theoretical lifespan ranging from thirty years and eleven months to forty-four years and two months; the species reaches sexual maturity between three years and nine months and six years and three months of age. The embryo develops inside an egg, which has a pear shape. The young are located on a rocky ledge, where parents feed them fish until they are able to jump into the water, with this stage lasting from two weeks and one day to three weeks and four days. An adult bird is capable of reproduction and spends much of its time in the open ocean, and the duration of the adult stage ranges from two to thirty years.