The Regent Parrot (eastern subspecies) primarily inhabits floodplain woodlands consisting of River Red Gumand Black Box. Nearby open mallee woodland or shrubland also provide important habitat for this subspecies. They often occur in farmland, especially if the farmland supports remnant patches of woodland along roadsides or in paddocks. The subspecies seldom occurs in more extensively cleared areas.
Nests are most often located in River Red Gum, and occasionally in Black Box, usually within 16 m of permanent water, or sometimes actually standing in water. Nest trees are typically large (>150 cm diameter at breast height and approximately 30 m tall). Generally, about one-third of nests are in dead trees, but there is much variation between sites and between years. Many breeding colonies, assumed to be traditional nesting sites, are in areas that have become drowned as a result lock and weir construction on the Murray River, although it is likely that birds have continued to nest at these sites in trees that are now dead.
There is a positive association between the position of Regent Parrot nest sites and the presence of large nearby stands of mallee vegetation. The proximity of major nest sites to large stands of mallee (within 20 km, though usually 5 to 10 km) reflects the dependence of the Regent Parrot on mallee vegetation as a feeding habitat during the breeding season, when they make two to three return trips each day between breeding sites in River Red Gums and foraging sites in mallee woodland.
The Regent Parrot forages in large stands of mallee vegetation that often comprise a shrub and herb layer not found in smaller mallee remnants, and it may be the presence of this understorey rather than the mallee trees themselves that is of importance to Regent Parrots They also feed in woodlands supporting Belah, Buloke and Cypress-pine. They occasionally feed within degraded shrubland vegetation dominated by Slender-leaf Hopbush ( Dodonaea viscosa ssp angustissima) and/or Berrigan ( Eremophila longifolia), as well as in farmland and along roadsides. Numerous records have also been made of Regent Parrots feeding in open ground near remnant vegetation.
As the Regent Parrot relies on mallee woodland for its survival, it is associated with a number of other threatened species which also inhabit mallee habitats in southeastern Australia, such as the Malleefowl, Major Mitchell's Cockatoo, Black-eared Miner, Hooded Robin, Southern Scrub-robin, Chestnut Quail-thrush, Crested Bellbird, Striated Grasswren and Red-lored Whistler.