Derbyan Parakeet

Lord Derby's parakeets are 45–50 cm (18–20 in) in length and are sexually dimorphic. They have a mostly green plumage over their dorsal surface (i.e. from behind), black lores and lower cheeks, a bluish-purple crown and pale yellow eyes. The throat, breast, abdomen and under-wing coverts are greyish blue to lavender. The thighs and vent area are yellowish green with blue edging on some of the feathers. The tail feathers are shades of green, some edged with blue. Male birds have a red upper mandible with a yellow tip, while the lower mandible is black. The females have an all-black beak. Immature Lord Derby's parakeets are duller in colour than the adults. Juvenile birds have green crowns, orange-red upper and lower mandible (beak), and their irises are dark and do not lighten until they reach maturity between two and three years of age.

Breeding season usually begins between April and June. The female lays a clutch of two to four eggs (36.1 mm × 27.7 mm [1.42 in × 1.09 in]) in nest holes of trees. The young hatch after an incubation period of about 23 days and will fledge after 8 to 9 weeks.