Corvids are believed to have reached the Americas via the Bering Land Bridge. Jays being the oldest corvids reached America first and rapidly spread south but have not yet reached the southern half of S. America. In most parts of the world corvids have received poor treatment from mankind, often being killed indiscriminately by grain and sheep farmers who were willing to blame huge losses on them. I a bounty was paid on their heads. They have been similarly persecuted in USA and Australia, yet still they survive and some species even thrive on and around human habitations, especially now that they are more protected by the law.
Jays are often colourful birds with many bearing various amounts of blue plumage.
Many species are socially monogamous, though at least 2 species in the genus Aphelocoma and Cyanocarax dicheyi have helpers at the nest which feed both the incubating female and the young. Most build nests in the branches of trees or shrubs except Lidth's Jay which makes uncharacteristically large nests in hollow tree. Both parents feed the young though the female is mostly responsible for nest building and incubation of the eggs. The main predators are humans, crows and squirrels. This survey was carried out on the temperate species Garrulus glandarius.