New research from Murdoch University has revealed that Carnaby's cockatoos depend on small, fragmented patches of native vegetation to survive in heavily cleared landscapes – a finding which could play an important role in protecting the endangered species.
Habitat loss and fragmentation is a primary driver of biodiversity decline worldwide and is one of many threats impacting Carnaby's cockatoos in Western Australia.
The research team, led by Dr Jill Shephard and Dr Zoe Kissane from the Harry Butler Institute, wanted to understand how the loss and fragmentation of habitat affected the movements of Carnaby's cockatoos during their breeding season.
"Carnaby's cockatoos usually breed between July and December and often return to the same breeding areas each year," Dr Shephard said.
"These breeding sites are critical habitat, so understanding how habitat loss affects their ability to find food is essential for their conservation" she said.
The team fitted GPS satellite tags to 18 wild Carnaby's cockatoos at five inland breeding sites across the Wheatbelt and tracked their movements throughout the breeding season.
The results showed that the birds in fragmented landscapes generally had to travel three times further each day to find food than birds living in less fragmented landscapes.
"The contrast between sites was striking," Dr Kissane said.
"At Coomallo, where native vegetation was heavily fragmented, birds were travelling more than 37 kilometres a day on average to find food. At Tenterden, where habitat remained more connected, they travelled just over 10 kilometres a day," she said.
"It shows that when Carnaby's cockatoos habitat becomes increasingly fragmented, the birds are forced to spend more time and energy moving between isolated patches of vegetation, which could have consequences for breeding success and population persistence."
The most interesting finding from the study was that small, degraded patches of native vegetation still appeared to be extremely important.
"We had suspected that small patches of remnant native vegetation were important for maintaining landscape connectivity for black cockatoos and our findings from this study confirm that to be true" Dr Kissane said.
"What might look like an isolated fragment of bushland can actually serve as a vital stepping stone, allowing Carnaby's cockatoos to move safely between larger habitat areas."
Dr Kissane said the study has practical implications for conservation management in WA.
"Conservation efforts have traditionally focused on protecting large, high-quality habitat, but our study shows that protecting the small patches are important too," she said.
Under the federal government's Black Cockatoo Referral Guidelines, the size and quality of a habitat patch determine whether a land-clearing proposal needs approval from the government regulator.
"Clearing less than 1 ha of foraging habitat, or less than 10 ha of low-quality habitat, is unlikely to require a referral," Dr Kissane said.
"However, our data show that black cockatoos regularly use small patches, including 'low' quality habitat, with patches considerably below these size thresholds, which suggests the current size cutoffs underestimate the value of small remnants and that the guidelines need revising," she said.
"If these small patches (1-10 ha) are increasingly and continually lost due to land clearing or climate change, there will come a point where the survival of Carnaby cockatoos at these sites will be no longer feasible."
The study, 'Landscape configuration influences home range size and migratory movements of Carnaby's cockatoos during the breeding season in fragmented mixed-use landscapes', was published in the journal Landscape Ecology .
