In a unique study of Perth and its surrounds, researchers have found the fragmentation of natural bushland is linked to an alarming decline in the numbers of native land birds.
Edith Cowan University's Rob Davis and his colleagues embarked on research in an effort to understand the impact Perth's rapid urbanisation was having on birdlife and to inform both landscape and local scale conservation planning.
"We found 54 bird species to be highly dependent on bushland, such as the scarlet robin and the splendid fairy-wren," Dr Davis says.
"We are seeing a worrying decline in their abundance and distribution that coincides with the eradication and fragmentation of their native habitat."
Skilled volunteers from Birdlife Australia surveyed bird communities on 121 sites each month for one year.
Sites ranged from across the Swan Coastal Plain and western Darling Range from north (Wanneroo) to south (Rockingham) and from west (Cottesloe) to east (Mundaring).
The sites encompassed a range of remnant land sizes and included urban landscape from the city, through suburban, semi-rural, and rural to largely uncleared native vegetation.
Dr Davis categorised the quality of each site, looking at its fire history and the amount of leaf litter and logs, indicating the insect numbers the birds need to survive.
For three groups of bushland birds, there were sufficient data to show their numbers were declining as the landscape became more fragmented.
"These birds were strongly correlated with the amount of vegetation within a 2km radius of where they occurred," Dr Davis says.
For three other groups of urban birds, their occurrences were either unrelated to the amount of vegetation cover or actually increased as the vegetation cover declined.
"Positively, we found 11 species that have adapted to urban environments and were found to be very common in both urban and vegetated landscapes," he says.
"The singing honey-eater, interestingly, is one of the few native species most likely to be found in urban areas."
The study recommends planners concentrate on maintaining the integrity and quality of remnant native vegetation, and aim at building public awareness of its conservation value.
"Rather than trying to connect already fragmented bushland, the focus should be on preserving and enhancing the already intact areas, such as Jandakot and the Darling Ranges," Dr Davis says.
"If we don't preserve these areas and consider the needs of our native birds, the most sensitive of them will be confined to landscapes outside of urban areas or their numbers will continue to decline until they no longer exist at all."
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