Superb parrots, whose numbers plunged through loss of habitat and their deadly practice of feeding on wheat on road edges, are back in the ACT's north-west and beyond.

The Canberra Ornithologists Group tapped into Commonwealth legislation to help guard the striking yellow and green parrot's habitat. Instead of developing land for 3500 dwellings in the new Gungahlin suburb of Throsby, the ACT government will make do with 1700.

COG president Chris Davey said the win was rare.

Mulligans Flat and Goorooyarroo Nature Reserves containing large intact yellow box - red gum grassy woodlands are other critical gains for native birds.

Yet conservationists are taking two steps back and one forward, according to Mr Davey. COG thought it had won a battle to preserve old yellow box gum trees at Crace, only to discover planners had drawn on a solar access edict that allowed the trees to be pushed down because they blocked sunlight.

''It's not until you have things on the ground that you have a win,'' Mr Davey said.

The Conservation Council ACT region and COG say Canberra's piecemeal planning should be replaced with a whole landscape view. COG's submission to a draft Molonglo Valley Plan says, ''We understand that the original management plan for Canberra Nature Park which included development of detailed plans for each reserve, has never been implemented.''

Mr Davey said there was no shortage of regulations and policies, but they were rarely implemented. New suburbs showed little commitment to maintaining old gums and spaces to accommodate birds.

A government spokesman said developers refer to design standards set by the government when determining street trees in the new Gungahlin and Molonglo suburbs. ''Where landscape proposals do not meet the criteria above, the developers are asked to provide alternative species and/or planting spacing.''

He said that, throughout Canberra, 54 per cent of trees in streets and parks were native, predominantly eucalypts. New suburbs continued with this percentage mix.

As far as possible groups of remnant trees were retained and individual trees assessed against criteria for the ACT Tree Register.

''Wildlife corridors are considered in broad-scale and local planning to connect these open space areas,'' the spokesman said. John Thistleton