<P> Breeding pairs must have a territory of their own before they begin nest - building and reproduction, and thus aggressively defend a territory and its food resources . Nesting territories vary in size according to the density of food resources in the area . The nest is a deep bowl made of large sticks and twigs, bound with an inner layer of roots, mud, and bark and lined with a softer material, such as deer fur . The nest is usually placed in a large tree or on a cliff ledge, or less frequently in old buildings or utility poles . </P> <P> Females lay between three and seven pale bluish - green, brown - blotched eggs . Incubation is about 18 to 21 days, by the female only . However, the male may stand or crouch over the young, sheltering but not actually brooding them . Young fledge at 35 to 42 days, and are fed by both parents . They stay with their parents for another six months after fledging . </P> <P> In most of their range, egg laying begins in late February . In colder climates, it is later, e.g. April in Greenland and Tibet . In Pakistan, egg - laying takes place in December . Eggs and hatchlings are preyed on, rarely, by large hawks and eagles, large owls, martens and canids . The adults, which are very rarely preyed upon, are often successful in defending their young from these predators, due to their numbers, large size and cunning . They have been observed dropping stones on potential predators that venture close to their nests . </P> <P> Common ravens can be very long - lived, especially in captive or protected conditions; individuals at the Tower of London have lived for more than 40 years . Lifespans in the wild are considerably shorter at typically 10 to 15 years . The longest known lifespan of a banded wild common raven was 23 years, 3 months . </P>

What time of year do ravens lay eggs
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