Mexican Jay Overview, All About Birds, Cornell Lab of Ornithology

In most populations of the Mexican Jay, young jays have large areas of white or flesh color on the basal half of the bill. It can take more than two years for the bill to turn entirely dark. These light areas on the bill may be asymmetrical and can be used by observers to identify individual jays.

Mexican Jay groups may number from 5 to 25 individuals, and may contain several active nests within one territory. Only the socially paired group members engage in nest-building, incubation, and brooding. All group members do virtually everything else, including alarm calling, mobbing, and feeding the young. Some jays feed at several nests within the territory, others feed at only one, and still others do not feed any young at all.

Genetic studies have shown that parentage within a Mexican Jay group is complicated, with most nests containing young sired by different males. Most of the extra-pair young were fathered by males within the group that did not help in nest building and did not appear to be paired.

In winter, Mexican Jay groups are often followed by Northern Flickers. The flickers pay attention to Mexican Jay alarm calls and are protected from predators by the vigilance of the jays.

The oldest recorded Mexican Jay was a male, and at least 17 years, 8 months old when he was identified by his band in Arizona in 1987. He had been banded in the same state in 1969.