For most plants and animals, just listing the family, genus or species is enough to let biologists know what the other levels should be. The most common way to list the taxonomic name of an organism is to list the genus and species; this is known as binomial nomenclature, meaning a two-name system.
The grey jay is a relatively large songbird, though smaller than other jays. A typical adult grey jay is between 25 to 33 cm (9.8 to 13.0 in) long. Its wingspan is around 45 cm (18 in). It weighs about 65 to 70 g (2.3 to 2.5 oz). Adults have medium grey back feathers with a lighter grey underside.
They are brightly colored, with a blue upper body, red breast, and white belly. Males have wing and tail feathers that are blue with black or gray shafts and tips. Females look similar to males, but are usually duller in color and are slightly larger. Adult eastern bluebirds weigh 27 to 34 grams. They are about 18 cm long from the tip of their beak to the end of their tail. Young bluebirds are grayish in color. They have speckled breasts and their wings have blue tips.