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Wednesday, March 21, 2012

Carnaby's Cockatoo suffers 37 per cent population decline in one year

Flocks of Carnaby's Black Cockatoo are iconic sights for the people of Perth, the Swan River Region and the forests of the South west. But comparing two population surveys in 2010 and 2011 showed a 37 percent decline in numbers across the Swan river region. That is a 37 per cent decline in one year.

According to Statistical modelling based on the 2011 Great Cocky Count the population of Carnaby’s cockatoos (Calyptorhynchus latirostris) in the Swan Region was between 5200 and 8600 birds. A year earlier it was estimated that the population was 8000 to 10,000.

Related: Scientific American - Endangered Australian Cockatoo Loses One Third of Population in Just 1 Year | Biodiversity crisis: Habitat loss and climate change causing 6th mass extinction

Found across south-western WA from Geraldton to Esperance, the species has declined across a third of its historic range: It no longer occurs in the central wheatbelt region. The numbers of Carnaby’s cockatoos have declined by at least 50 per cent over the past 45 years. The Swan Region is considered core feeding habitat for northern and western populations of over-wintering cockatoos.

It is listed as Endangered under the International Union for Conservation of Nature (IUCN) Red List, Endangered under the federal Environment Protection and Biodiversity Conservation Act 1999 and as rare and likely to become extinct by the WA State Wildlife Conservation Act 1950.

Dr Ron Johnstone, WA Museum’s ornithology curator and Adjunct Professor at Murdoch University said in May 2011 that the bird's existence is likely to become more precarious as they shift their breeding grounds from the Wheatbelt to around Perth. The breeding location shift has been occurring since World War II as a result of large scale land clearing in the wheat belt, and has accelerated in the last 3 decades by climate change and competition for food and nesting hollows with galahs and other cockatoos and bees.

Their demise has many contributory causes including:

  • habitat loss caused by human development and woodland and heathland clearances for agriculture and forestry,
  • extreme weather events like severe heatwaves and hail storms which are becoming more frequent with climate change,
  • fatal impacts by vehicles,
  • severe drought and bushfires reducing available foods and causing loss of habitat

BirdLife Australia’s WA Program Manager Cheryl Gole warned in an 8th March media release (PDF) of the threat of further human development and habitat destruction in the Perth region. "WA's Swan Region is the core feeding habitat during winter for northern and western populations of Carnaby’s Cockatoos. Increasing habitat clearance and fragmentation is the biggest threat to this cockatoo. Recent forecasts for the Perth and Peel region indicate that there will be a larger human population than previously predicted by 2026. This is going to further increase the need for housing and land and increase the pressure on cockatoo habitat. Birdlife Australia believes all habitat used by the cockatoos that remains in the Perth and Peel region is needed for the survival of the birds. We need to strike a balance, and act decisively and quickly to conserve what we have left."

Conservation Council of WA spokesman John McCarten said in a media release the same day, “To lose more than a third of an endangered species in just one year is a devastating result and shows that current conservation measures are failing. In the Perth Metro area alone we lost 34% of our Carnaby’s – that’s an awful figure for the many people who appreciate their contribution to the unique feel of our city."

"Carnaby’s Black Cockatoos are a federally protected endangered species and a true WA icon. There are so few places in the world where a critically endangered species lives side-by-side with a million people, but in Perth we have that with the Carnaby’s. We can’t control the weather, so it is vital we do all we can to preserve the remaining cockatoo habitat and halt this alarming decline in numbers. This means regulating development, controlling pests, exercising caution when approving prescribed burns and ending native forest logging."

As is to be expected, a spokeperson for the Institute of Forresters of Australia (WA Division) took umbrage at the conservationists calling for an end to native forest logging.

"Conservationists have been blinded by their own ideology" said John Clarke, chairman of the WA Division of the Institute of Foresters of Australia. "The Great Cocky Count 2011 report states that the likely reasons for the decline in numbers include clearing of woodland habitat, loss of habitat through Phytophthora dieback, the drought of 2010/11 and the massive hailstorm of March 2010."

“And, as graphically portrayed in a television documentary this week, shooting and vehicle hits continue to take their toll.”

“Carnaby’s cockatoo is a bird that lives predominantly in the woodlands of the wheatbelt and the coastal plain. It is not threatened by sustainable timber harvesting in south west forests” said Mr Clarke.

“By misdirecting the attention away from the real causes of Carnaby’s cockatoo decline the Conservation Council is deluding the public which would be mistaken in thinking that changes in timber harvesting would have any effect.”

“I am very concerned that they are blinded by their own ideology” said Mr Clarke. “Help for Carnaby’s cockatoos needs to be based on science, not prejudice.”

John Clarke picked up McCarten's concluding statement about "ending native forest logging" as incorrect about the Carnaby's Black Cockatoo and used it to justify logging of native forests. Carnaby's Cockatoo is an occasional visitor to the dense Marri, Karri and Jarrah forests, but these same forests are the prime habitat for two other endangered species of cockatoo: Forest Black Cockatoo also called Baudin’s Cockatoo (Calyptorhynchus baudinii) and Forest Red-tailed Black Cockatoo (Calyptorhynchus banksii naso). Forests such as the Warrup currently being logged also contain other endangered species such as the Numbat which is on the IUCN redlist with an estimated total population of about 1,000.

Timber harvesting has been implicated for the population decline of both these bird species as noted in the 2008 Recovery plan:

Habitat loss for agriculture, timber harvesting, wood chipping and mining appears to be the principal cause of the historical decline of Baudin’s Cockatoo and the Forest Red-tailed Black Cockatoo (Johnstone 1997; Mawson and Johnstone 1997). The long-term effects of this habitat loss may not yet have been fully realised because of the long life-span (Brouwer et al. 2000) of the cockatoos.

In the remaining habitat, selective removal of Marri for timber, mining, wood chipping and agriculture has resulted in further declines (Garnett and Crowley 2000, personal communication P. Mawson2). The impacts of previous forest management practices for timber and wood chipping on Forest Black Cockatoo populations have not yet been quantified. However, forestry practices such as clear felling and 80-year cut rotations may restrict the availability of nest hollows (Saunders and Ingram 1995).

So what does the science say about Carnaby's Cockatoo? I checked the latest survey report - 2011 Great Cocky Count: Population estimates and identification of roost sites for the Carnaby’s Cockatoo (Calyptorhynchus latirostris) (PDF). Here is what this report says under habitat:
Carnaby’s Cockatoo occurs in native woodlands, typically dominated by Salmon Gum Eucalyptus salmonophloia) and Wandoo E. wandoo, and in shrubland or heathland dominated by Hakea, Banksia (including Dryandra) and Grevillea species (Cale 2003). They are frequently reported in remnant patches of native vegetation on land otherwise cleared for agriculture (Saunders 1979b, 1982, 1986) and seasonally inhabit pine plantations (Davies 1966; Saunders 1974a; Sedgwick 1968, 1973), and forests containing Marri, Jarrah or Karri (Nichols and Nichols 1984; Saunders 1980). Carnaby’s Cockatoo is occasionally recorded in casuarina woodlands or mallee (Carnaby 1933; Nichols and Nichols 1984), and is often recorded in towns or on roadside verges and in gardens around Perth that contain both native and exotic plants (Sedgewick 1973; Saunders 1980).

The habitat of Carnaby’s Cockatoo became severely fragmented during the mid-twentiethcentury due to the clearing of native forest, woodlands, shrublands and heathlands for agricultural and suburban development. Today, much of the remaining native habitat occurs in isolated remnant patches (Saunders 1990; Saunders and Ingram 1998).

Dr Denis Saunders highlighted the problem in his 1990 scientific paper published in Biological Conservation - Problems of survival in an extensively cultivated landscape: the case of Carnaby's cockatoo Calyptorhynchus funereus latirostris (abstract).
The south-west of Western Australia has undergone recent and extensive clearing of its native vegetation to develop agricultural enterprises. In some areas, over 90% of the original vegetation has been removed and the remainder is scattered in numerous patches of varying size, shape, degrees of isolation and degradation. There have been marked changes in the distribution and abundance of the avifauna of this area, with some species disappearing from parts of their former range and others expanding their ranges to take advantage of the altered landscape.

Saunders identified that "extensive removal of native vegetation, patchy distribution of food and interactions with species like the galah Cacatua roseicapilla and man are contributory factors to its decline".

It is pretty clear that the south west forests are part of the bird's habitat, with the vegetation clearances of mature trees in the wheatbelt having pushed many to compete for tree hollows in established forests. That would include native forests being logged, particularly where it says "seasonally inhabit... forests containing Marri, Jarrah or Karri" which are sought after native forest hardwood timbers. Timber harvesting may not be the most important factor affecting this species decline, but neither can you say that logging native forests is not having an impact as the bird utilizes a range of habitats for nestling, roosting and foraging which does include mature native forests.

Caption: Carnaby's Black Cockatoo indicative distribution as of 2009 showing in dark brown the breeding range, and light brown the wider foraging and non-breeding range.

Changing Climate and Impact of Extreme Events

In recent years extreme weather events have caused fatalities in the Carnaby’s Black Cockatoo population. The South West of Western Australia shows a pronounced drying trend with hotter summers with more heatwaves, and more intense storms due to climate change. This has impacted on Carnaby's Cockatoo.

A scientific paper by Denis Saunders, Peter Mawson and Rick Dawson in Pacific Conservation Biology published in June 2011 - The Impact of Two Extreme Weather Events and Other Causes of Death on Carnaby's Black Cockatoo: A Promise of Things to Come for a Threatened Species? (abstract) detailed and discussed the implications of climate change and severe weather events to this species. The abstract said:

Carnaby's Black Cockatoo is an endangered species which has undergone a dramatic decline in range and abundance in southwestern Australia. Between October 2009 and March 2010 the species was subjected to a possible outbreak of disease in one of its major breeding areas and exposed to an extremely hot day and a severe localized hail storm. In addition, collisions with motor vehicles are becoming an increasing threat to the species. All of these stochastic events resulted in many fatalities. Species such as Carnaby's Black Cockatoo which form large flocks are particularly susceptible to localized events such as hail storms, contagious disease and collisions with motor vehicles. Extreme temperatures may have major impacts on both flocking and non-flocking species. Predictions of climate change in the southwest of Western Australia are that there will be an increased frequency of extreme weather events such as heat waves and severe hail storms. The implications of more events of this nature on Carnaby's Black Cockatoo are discussed.

Dr Saunders commented on the devastating impact of the severe thunderstorms of 2010, “We know that 81 were affected by the hail – 57 were killed and 24 were so badly injured with soft tissue and skeletal damage they would have to go into rehab,” he said in an article on Science Network WA. Most of the dead birds were found in Kings Park and Subiaco where the storm hit hardest.

Hot weather and heatwaves also impacts the bird's ability to forage and feed. “Their foraging time gets reduced because they can only forage early in the morning or late in the afternoon,” he says. In an incident near Hopetoun in January 2010 145 dead Carnaby's Black Cockatoos were found after an extreme heatwave. "The problem is that while they were shaded from the sun they were exposed to hot winds of over 50c," Dr Saunders said. "The only way they can cool down at that stage is to spread their feathers and try and shed heat—but what affectively happens is that they cook."

The bird species, with a limited geographical area, is also susceptible to disease outbreaks. An unknown disease outbreak killed as many as 23 female Carnaby’s Black Cockatoos at Koobabbie a property near Coorow, late in 2009. Normally there are 30 nesting pairs on this property producing as many as 19 fledglings per year.

The scientific research showed that fatalities arising from collisions with motor vehicles is also increasing. We have cleared much land for development and agriculture, but have left remnant vegetation along road sides where cockatoos are likely to feed. “The birds tend to fly out into clear areas to get airborne,” said Dr Saunders.

The future for Carnaby's black cockatoo and related cockatoo species is looking pretty bleak. Dr Ron Johnstone, WA Museum’s ornithology curator and Adjunct Professor at Murdoch University, said in January 2012, that the species could be extinct within 50 years. “They are iconic large forest cockatoos that were once widespread and common in huge numbers on the Swan Coastal Plain,” he said in a Science WA article, “It’s been death by a thousand cuts as the vegetation has been reduced.”

The other species affected and also on the IUCN redlist include Baudin’s Cockatoo (Calyptorhynchus baudinii) and the Forest Red-tailed Black Cockatoo (listed as Vulnerable under the EPBC Act) (Calyptorhynchus banksii naso). All three species nest in tree hollows, and move south and west after nesting season to feed on nuts, nectar and wood-boring grubs and insects, including nuts from pine plantations (Pinus radiata).

As the banksia heathlands have been destroyed with the development of Perth's suburbs, pine plantations have provided a partial food replacement. As pine plantation mature and are harvested, this leaves the cockatoos with dwindling foraging opportunity. “Even where the plantations are removed we should try and keep at least a fringe of pines that will provide food which will allow the birds to adjust a bit.” said Professor Johnstone.

He has also advocated a proactive urban planning policy that includes planting suitable trees and shrubs and maintaining mature trees as part of urban developments to provide food and roosting for cockatoos while new trees grow to maturity.

Dr Denis Saunders advocated 20 years ago that native vegetation corridors should be established which would significantly improve survival of native wildlife. He said in his 1990 scientific paper "It is pointed out that some local disappearances of this species may have been avoided if corridors of native vegetation had been left across the landscape to link remnant patches. These could have channelled Carnaby's cockatoo to areas of native vegetation which provide its food. Not only is it important to retain linkages between remnants of native vegetation but there is a need to re-establish corridors of native vegetation in extensively cleared agricultural areas such as those in the wheatbelt of Western Australia."

So where does all this sit with the politicians in WA?

Environment Minister, Bill Marmion has said there is no scientific evidence to suggest that logging activities in native forests were putting the black cockatoos at risk. The Forresters clearly agree.

But this is disputed by the Conservation Council of WA. We are not talking primarily about Carnaby's black cockatoo here, but the equally threatened Baudin’s Cockatoo and Forest Red-tailed Black Cockatoo.

"The evidence that was brought up in the Government’s 2008 cockatoo recovery plan says conservation of feeding and breeding habitats of forest black cockatoos relies on the protection of marri, karri and jarrah habitats,” Conservation Council of WA spokesman Mr McCarten said in a Perth Now report.

That 2008 recovery plan refers to Baudin’s Cockatoo and Forest Red-tailed Black Cockatoo, both of which inhabit the humid and sub-humid dense forests of south-west of Western Australia, not Carnaby's Cockatoo who appears to be just an occasional visitor to these forests. Both of these species are dependant on forest habitats, primarily of Marri, Karri and Jarrah, and have suffered substantial population declines due to timber harvesting and clearing for agricultural land use over the last century.

"If we're clearing marri and jarrah habitat, which we necessarily are by logging, then we're definitely going to be affecting cockatoo numbers. We're coming out of a very big drought; the fires have devastated the cockatoos' habitat, and they're not doing well." said McCarten

So Forresters spokeperson John Clarke, and Environment Minister Bill Marmion are mostly right that logging native forests is not the main culprit driving the decline in population of Carnaby's Black Cockatoo - human land use, agricultural clearing, vegetation changes and urban development are probably the main drivers.

But logging of native forests will have a major impact on the other two species of black cockatoo, both of which are also endangered and suffering population declines due to habitat loss (logging), illegal shooting, nest hollow shortage and competition for available nest hollows, and severe weather and climate change impacting biodiversity and ecosystem function.

Sources:

Posted by takvera (John Englart) at 4:15 PM
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