Snowy owls are generally monogamous, though polygyny has been reported in a few instances when prey was excessively abundant. Breeding pairs may form on the wintering ground or after the owls reach the breeding ground in late April or early May. There is no evidence that pair bonds last beyond one breeding season.
Elaborate courtship displays are associated with breeding pair formation and early breeding activities. The male performs an “aerial display” followed by a “ground display’. The “aerial display” consists of an exaggerated undulating flight, frequently while carrying a lemming in the bill or claws, followed by a gradual climb and finally a gentle vertical descent to the ground. Once on the ground, the male performs the “ground display”. With his back toward the female, the male stands erect and then leans forward with his head lowered and tail partly fanned until he is nearly lying on the ground. Another infrequently observed display is the passing of a lemming from male to female while in flight.
Mating System: monogamous
Snowy owls usually breed between May and September. Individuals arrive on the breeding grounds beginning in late April, though breeding pairs may form earlier on the wintering grounds. The male of a pair establishes a territory, and the female selects a nest site, which is a low windswept prominence, such as a hillock, hummock or boulder. The female constructs a nest by scraping out a shallow bowl in the turf or bare ground. The nest is not lined with any insulating materials. The female then begins laying eggs at 2-day intervals. Clutch size is usually 3 to 11 white eggs, depending on prey availability, but can be as large as 16 when prey are extremely abundant. The female incubates the eggs, beginning with the first egg laid. The chicks hatch asynchronously after 32 to 34 days (average 31.6 days) of incubation. The eggs hatch approximately every other day leading to a wide range in size and age of chicks within a nest. The female broods the chicks until they abandon the nest. Both parents feed and protect the chicks, which are covered with snowy white down. The male brings food to the nest, where the female dissects it into smaller pieces to feed to the chicks. Chicks begin to leave the nest before they can fly, 14 to 26 days after hatching. The parents continue to feed them for 5 to 7 weeks until they are able to hunt for themselves.
The age of sexual maturity is not known for this species, though it is likely to me at least two years old. Adult snowy owls are able to breed annually if prey abundance allows. In years of low prey abundance, snowy owls forgo breeding. Snowy owls generally raise only one brood per breeding season. However, if a nest fails early in the breeding season, snowy owls may re-nest.
Breeding interval: Snowy owls breed once annually if sufficient prey are available.
Breeding season: Snowy owls breed between May and September.
Range eggs per season: 3 to 16.
Range time to hatching: 27 to 34 days.
Average time to hatching: 31.6 days.
Range fledging age: 14 to 26 days.
Range time to independence: 5 to 7 weeks.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate)
Average eggs per season: 6.
Snowy owl females lay and incubate the eggs for an average of 31.6 days. After hatching, the female broods the semialtricial chicks until they leave the nest at age 14 to 25 days. Both parents defend the nest by dive-bombing potential predators that approach the nest and using distraction displays to draw the predator away from the nest. The male brings food to the nest for the chicks. The female processes the food by tearing it into smaller pieces before feeding it to the chicks. After the chicks leave the nest, both parents continue to feed and protect the chicks for 5 to 7 weeks.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Protecting: Male, Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female)