Three threatened black cockatoos inhabit the Jarrah Eucalyptus marginata-Marri Corymbia calophylla forest of southwestern Australia: Baudin’s Cockatoo Calyptorhynchus baudinii, Carnaby’s Cockatoo C. latirostris, and Forest Redtailed Black Cockatoo C. banksii naso [FRTBC]. Their local ecology in relation to anthropogenic disturbance is poorly known, hampering effective conservation management. Therefore we studied their group size, site occupancy patterns, habitat use, and food plants at a mine-site and its surrounds in the eastern forest over three years. FRTBC showed similar group sizes and occupancy across seasons, suggesting year-round residency and no marked seasonality in movements and grouping patterns. In contrast, Carnaby’s Cockatoos were up to twice as abundant in spring and summer, indicating migrating or transient flocks and some year-round residents. Few Baudin’s Cockatoos were present in summer, but their abundance increased at other times. All three cockatoos were observed in modified or humanmade habitats such as mine-site rehabilitation, farm paddocks, and pine plantations. Carnaby’s Cockatoos used the broadest habitat range. We documented feeding on 16 plant species, with Carnaby’s Cockatoos eating at least 10. Examination of feeding residues as well as observations of behaviour were essential to obtain a complete picture of feeding. Current mine-site rehabilitation protocols provide food for all three black cockatoos within a decade and should continue to do so long-term if Marri is maintained in the seed mix. However, because climate change scenarios predict declining rainfall over much of southwestern Australia, the plant species used to revegetate mine-sites and other landscapes may need to be reconsidered. For areas that do not specify restoring a jarrah forest landscape, the selective use of exotic or non-endemic flora better adapted to lower rainfall conditions may be an option.