The main predators are humans, crows and squirrels. This survey was carried out on the temperate species Garrulus glandarius. Young Jays leave the nest after about 3 weeks. Jays are generally omnivorous feeding on seeds, fruits and insects though some species such as the European Jay and the Pinan Jay have specialised on plant seeds, Oak acorns and Pinan Pine seeds respectively. In most species breeding commences at one or two years of age but the social breeding species and the European Jay take at least 3 years to reach sexual maturity.
Several species have numerous subspecies and wide distributions.
The Scrub Jay has 17 or 18 recognised subspecies. Most species are sedentary living in pairs or small groups outside of the breeding season. Blue Jays, however, congregate into large flocks and migrate about 100 miles south. Most Jays hop instead of walking. Magpies are believed to have evolved from a Jay-like ancestor and the 'pie' in Magpie and Treepie refers to the black and white or pied plumage of many of them.