It is not known when northwestern crows (Corvus caurinus) form breeding pairs, but it is most likely sometime in their second year, prior to the breeding season. If a courtship display exists, it is very subtle and has not been observed. However, prior to copulation, the male droops, spreads his wings and tail, points his bill down and quivers his wings and tail while exposing nictitating membranes (a transparent inner eyelid in birds). The female has a similar display, but she crouches and quivers her tail rapidly.
Corvus caurinus has been known to participate in cooperative breeding. A mated pair will sometimes keep one of their offspring from the previous season (who has not yet reached sexual maturity) with them on their breeding territory. The juvenile bird helps the male protect the territory, hide food, and, very infrequently, gather food for the nestlings. A breeding pair does not always have a helper; when they do they only have one and it is always one of their offspring.
Mating System: monogamous ; cooperative breeder
Young Corvus caurinus probably reach sexual maturity between 15 and 20 months. They copulate and begin building nests from early February through late March. Northwestern crows breed once yearly, but they will renest if disturbed early in the season. The female selects a place to build the nest, normally in or under trees, shrubs, blackberry tangles, or tall grass. Nest-building occurs only during daylight hours and in good weather. Nests are built with branches broken off of trees, grass and moss as well as other objects and soil. Corvus caurinus line their nests with moss, gull and crow feathers and sheep's wool, among other things.
A female C. caurinus typically lays 3 to 6 eggs per breeding season, laying one egg a day, almost always before 8:00 AM. Eggs are pale bluish with darker brown spots and are subelliptical to oval. They have a smooth, slightly glossy surface and are about 40 mm long and 28 mm wide.
Incubation most likely begins on the second day, and is performed by the female only. The incubation period is about 18 days; during this time the male feeds the female, most often at a small distance from the nest. After the eggs have hatched, female C. caurinus begin feeding the hatchlings.
Corvus caurinus typically leave the nest permanently at about 31 days. All of the chicks leave the nest on the same day and stay in nearby trees and shrubs, making short flights when their parents are away. They begin exploring nearby territories between 10 and 14 days and begin feeding themselves as early as 55 days after hatching. Parent C. caurinus will feed fledglings until they are 77 days old.
Breeding interval: Northwestern crows breed once yearly, but they will renest if disturbed early in the season.
Breeding season: Corvus caurinus copulate and begin building nests from early February through late March.
Range eggs per season: 6 to 3.
Range time to hatching: 20 to 17 days.
Range fledging age: 35 to 29 days.
Average time to independence: 77 days.
Range age at sexual or reproductive maturity (female): 15 to 20 months.
Range age at sexual or reproductive maturity (male): 15 to 20 months.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization
Average eggs per season: 4.
Adult C. caurinus build nests for their young, then lay eggs. The female broods the altricial young for about 18 days before devoting all of her time to gathering food and feeding them. The male, and sometimes a helper, will bring food from the time they hatch, until about 77 days after hatching. Young leave the nest at about 31 days but still rely on their parents for food as they can only make short flights. They begin to feed on their own starting around 55 days and parents generally stop feeding them at 77 days. Parent birds protect their offspring throughout this time. Immature C. caurinus associate with roosting groups of adults and feed near them for the first year or two, probably to pick up their leftovers and learn the intricacies of feeding.
Parental Investment: no parental involvement; altricial ; pre-hatching/birth (Protecting: Female); pre-weaning/fledging (Provisioning: Male, Female, Protecting: Male, Female); pre-independence (Provisioning: Male, Female, Protecting: Male, Female); post-independence association with parents