Experts say the urban sprawl and removal of large gardens for in-fill development is forcing birds away from residential areas in Western Australia.

A record number of bird watchers have taken part in a national citizen science project documenting bird populations near residential areas to try to determine any trends.

More than 1.4 million birds were counted in the Aussie Backyard Bird Count, which is in its third year this year.

Retired ornithologist and Cape to Cape Catchments Group Chair Boyd Wykes has been carefully tagging and documenting the bird life he finds in the Margaret River region for the past 16 years and said some breeds no longer visited.

His lush garden, with a diverse range of tall native trees, bushy shrubs and flowers, is designed to be a pit stop for birds travelling from nearby bushland.

"[Gardens are] an extension of the habitat," Dr Wykes said.

"When we've got remnant vegetation, forest, streams, the gardens connect those."

"[Birds] can come here as a refuge in the summer when there's no water in the nearby bush, when we've burnt an area, or a wild fire's burnt it, there's a population of birds that can still be living in our gardens."

Dr Wykes said he worried about the impact urban in-fill could have on bird habitats.

"I think the hardest thing is in-filling where we've had large blocks and then if we put another house on the back of that block, and lose the vegetation it had."

"And [if] you get a large enclave like that, then the birds can't move through, you've got your fences, you've got your cats, you've got your dogs," he said.

"We need those tall trees and they can get old and sick when they're isolated, so one of the things we'll continue to monitor is whether that habitat that's now supporting birds is deteriorating over time."

A splendid fairy-wren enjoys the habitat a flowery shrub provides. ( Supplied: Boyd Wykes )

Dr Wykes said while governments did have a large responsibility to protect bird habitats, there was a lot that householders could do too.

He suggested planting native, bushy plants that provide food, shade and nesting sites, plant verge gardens and keep cats indoors.

"I see trees chopped down just because they put too many leaves in the gutters," Dr Wykes said.

"We need to maximise the habitat for our wildlife while making it a very pleasant place for us to live."

"Fortunately shade is something that's good for us."

BirdLife WA claimed their research suggested urban sprawl and in-fill was having a damaging effect on bird populations near residential areas.

"Traditional urban sprawl where we bulldoze bushland and put in McMansions, that's devastating," chairman Mike Bamford said.

"You end up with three bird species where there were 60 bird species, and those three are magpies, raven and magpie larks maybe."

Mr Bamford said the clearing of native vegetation for housing was coming to an end in Perth, claiming it was one of few places in the developed world still doing it.

"We would've stopped years ago [but] because it's biodiverse banksia woodland which doesn't look spectacular to some people, we've sort of carried on clearing but we're coming to an end of even clearing that, thank goodness."

"Now we're looking at urban in-fill as a way of fitting more people in, making better use of land.

"The challenge is creating urban in-fill that's green, has green space in it that will support the birds and create that pleasant environment for birds and for people," Mr Bamford said.

A kookaburra sits in this old gum tree. ( Supplied: Boyd Wykes )

Many bird species in decline

In August last year, the Environmental Protection Authority advised the State Government the environmental cost of continuing the urban sprawl was incalculable and that strategic land use planning was needed to ensure the environment was not further compromised by population growth.

"On the Swan Coastal Plain, which is west of the scarp, 71 per cent of vegetation has been cleared and our wetlands, estuaries and waterways are showing signs of ecological stress," the chairman at the time, Dr Paul Vogel, said in his advice.

"A number of the original species that were present in the Perth-Peel area at the time of settlement have disappeared from the region, including 12 mammals such as the numbat, brush-tailed phascogale, western ringtail possum, and pygmy possum."

"There are 46 bird species in decline and many of the plants are also now restricted and threatened with extinction."

Dr Vogel recommended the government conserve important areas of remaining native vegetation and plant more trees to improve air quality and temperature in urban areas.

The State Government is now finalising a strategic conservation plan as part of its growth plan for the region.

BirdLife Australia held the Aussie Backyard Bird Count last week to build a snapshot of bird populations in urban areas.

It required people to spend 20 minutes in their garden, local park or beach identifying the birds they could see and listing them in the Aussie Bird Count app or on the website.

There were 652 species of birds identified across Australia in the count this year.

BirdLife said the count gave an indication of the health of the environment.