The most common time for mating is either morning or evening. Birds indicate readiness by head flicking, which may be done either on land or in water. During this display, the bill may be open or closed. Members of a pair may mutually bow or put their bills side by side. Horned puffins form monogamous pairs.
Males may perform a swim display in which they raise themselves from the water and extend their necks upwards. Then they flick their heads, and at this time mounting is often observed. Mating takes place mostly in water with some rare cases on land.
Mating System: monogamous
The general reproductive behaviors of horned puffins are not as well known as those of most auks. Birds arrive in the breeding colonies between April and May. Colonies are usually small. The nesting sites are on steep slopes or cliffs, and nests are usually separated by a distance of 1.5 meters. The nest itself may be in a burrow, in a rock crevice (usually), or under a boulder. It is lined with feathers, grass, or debris collected by both sexes.
A mating pair produces one egg, which is oval in shape. If the egg is lost it is replaced in 10 to 21 days. The egg itself is gray with purple dots, a type of spotting that suggests an ancestral habit of laying eggs out in the open. Horned puffin eggs quickly become covered in guano and other debris. They incubate for around 41 days, and both males and females participate in caring for and incubating eggs.
After the egg is hatched, parental care continues for 6 days. Feeding of a chick is done during the day by both parents. The chick becomes able to manage its own body temperature between 5 and 6 days after hatching. After this and for the next 35 days, the chick is left alone in the nest while both parents bring it food. There is no evidence of post-fledging care and the chicks depart at night by themselves. Horned puffins reach reproductive maturity between 3 and 5 years of age.
Not much is known about the molting process besides that it takes place in autumn to winter, and bill ornaments are dropped at the end of caring for the chick.
Like some other marine birds, females have sperm storage glands. It is not known if they are functional.
Breeding interval: Horned puffins breed once yearly.
Breeding season: Horned puffins breed from April to July.
Average eggs per season: 1.
Range time to hatching: 40 to 42 days.
Range fledging age: 34 to 40 days.
Average fledging age: 35 days.
Range age at sexual or reproductive maturity (female): 3 to 5 years.
Range age at sexual or reproductive maturity (male): 3 to 5 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sperm-storing
Female horned puffins lay a single egg in the spring, which is incubated by both parents for 41 days. After the egg hatches, the parents tend the chick closely for the next week. The chick is born altricial, but is able to thermoregulate a little over a week after hatching. After that, the chick is left alone in the nest for the next 37 to 46 days while being attended by the parents only for feeding. Pairs defend their nests and males defend their mates. Males show a threat display and fight if provoked.
Parental Investment: altricial ; male parental care ; female parental care ; pre-fertilization (Protecting: Male, Female); pre-hatching/birth (Provisioning: Male, Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)