"It's important to build on last year's count when we found there had been a 15 per cent decline in the birds" numbers," count co-ordinator Matt Byrne said.
Volunteers will count endangered Carnaby's and Baudin's black cockatoos in Perth and the South West, including at prime roosts at Underwood Avenue in Shenton Park and pine plantations in Bentley, Murdoch and Gnangara.
The State Government lists Carnaby's cockatoos as rare or likely to become extinct after their population halved in 45 years due to clearing bush in the Wheatbelt, fewer old trees for nest holes, degraded feeding areas and urban sprawl on the Swan Coastal Plain.
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READ NOWMr Bryne said the April 12 count needed people to travel to the South West and Wheatbelt to visit roost sites.
The count is on April 12. Email wa@birdlife.org.au or call 9383 7747.