At three years of age, jays begin to breed. In spring, gatherings known as 'crow marriages' may occur, which allow unpaired birds to find a mate. The nest is built in a tree towards the end of April; it measures up to 30 centimetres across, and consists of twigs lined with fine roots, grass and hair. The courtship display involves much posturing, with wings and tail outstretched. After mating the female lays between five and seven glossy eggs, and both the male and the female take turns to incubate them for 16 days (6). Following hatching, the chicks are fed by both parents for around 20 days. After the chicks leave the nest, a close bond remains with the parents, who continue to feed them and stay with them throughout the autumn (6).
Acorns are the most important component of the diet; these are buried during autumn to provide a cache of food for more harsh times of year, and it is widely believed that jays play a crucial role in the spread of oak woodlands (6). Several thousand acorns are stored by a single bird each autumn (8). They also feed on grains, invertebrates, beech nuts and sweet chestnuts during winter (8), in the spring they feed on caterpillars (6), and eggs are taken during summer (2).
Jays attack crows, owls and hawks, mobbing them whilst mimicking their calls as an alarm (6). Anting behaviour has been observed in this species; ants are encouraged to swarm over the bird's body and the jay seems to enjoy this immensely (6).