Cassin's Auklet Overview, All About Birds, Cornell Lab of Ornithology

The Cassin's Auklet is the only alcid known to produce two broods in a single breeding season, at least in the southern part of the range where birds may be seen at nesting colonies every month of the year.

Vulnerable to predators, especially large gulls, the Cassin's Auklet tends to visit its nest at night.

The oldest recorded Cassin's Auklet was at least 16 years, 2 months old when it was found in California in 1993. It had been banded in the same state in 1978.