Carnaby's black-cockatoo

Cocanarup’s Carnaby's

Carnaby’s first appear in Cocanarup in June/July and nesting and raising young takes place through spring and into summer. The earliest confirmed nesting record is in the first week of August and the latest record of adults feeding young is in the first week of February. Once the young birds are ready, the birds leave Cocanarup and fly the 35-plus km to the south coast and spend the non-breeding season there.

They feed on the extensive area of botanically diverse and “cockie-food-abundant” banksia shrublands which dominate this very important coastal corridor of vegetation stretching through the Fitzgerald River National Park to well east Hopetoun. Then, at the end of each day the birds fly to a suitable roost site, which can be many kilometres from their feeding area. Over the years, some roost sites have been located and they include trees along the Oldfield, Jerdacuttup, Steere, Phillips and West Rivers. In this region, the use of roost sites appears to be opportunistic, rather than birds consistently using a particular site – however, having fresh water nearby appears to be a consistent requirement.

In April 2019, flocks of up to 800 birds were regularly recorded flying just before sunset in a north-westerly direction from east of Jerdacuttup Lakes to a place on the Steere River, where there are suitable roost trees and presumably fresh water. This roost site is within the proposed Cocanarup – Kundip Class A Reserve.

Critical habitat requirements

The combined critical habitat requirements of the local Carnaby’s include:

• the coastal vegetation for non-breeding feeding grounds,
• large trees for roosting - mainly swamp yates (Eucalyptus occidentalis) but also introduced pinus species - which grow along the rivers, around wetlands and on farms,
• fresh water for drinking near roost sites and nesting sites – from springs in the rivers, or agricultural dams etc.,
• large hollows for nesting – found in mature salmon gum woodland,
• and feeding grounds close to the nest sites.

All of these habitat requirements need to be safeguarded for the local population of Carnaby’s to survive and thrive. To protect Carnaby’s requires protecting the whole wonderfully diverse patchwork of vegetation and resources that characterise this area.

The Cocanarup salmon gum woodland is the most specialised and non-replaceable of the resources required by Carnaby’s. The woodland, which comprises several distinct areas, is estimated to be about 1000 ha in extent. It is the most extensive patch of salmon gums in the region and, most importantly, it has large mature stands of trees which have developed numerous hollows large enough for use by nesting Carnaby’s. Much of the other salmon gum woodland in the district was cut over for mining in the early 1900s or has been otherwise disturbed, and has not developed hollows. There is simply no equivalent stand of trees in the region. Another invaluable feature of the Cocanarup nesting site is that it is surrounded by intact vegetation which provides the necessary forage areas for breeding birds.

The following plants are known to provide food for Carnaby’s in the Ravensthorpe-Hopetoun area:

Banksia speciosa, B. baxteri, B. lemanniana, B. media, B. blechnifolia, B. repens, Hakea corymbosa, H.cinerea, H.laurina, H.lissocarpha, H. victoria, H. verrucosa, H. preissii, H. newbeyi, Eremophila glabra, Eucalyptus pleurocarpa, Acacia cyclops, Allocasuarina huegeliana, Callitris sp and introduced species: storksbill, cape-weed, radish, canola, Pinus pinaster and P. radiata. Birds also feed on large wood-boring grubs found in the trunks of Acacia cyclops and Allocasuarina huegeliana. They also regularly feed on plants growing in the gardens of Hopetoun which include a range of non-local banksias and hakeas etc.

Known threats

Known threats to local Carnaby’s as listed in the Fitzgerald Biosphere Recovery Plan (2012), include:

• Loss of breeding and feeding habitat, including suitable nest-hollow trees;
• Fragmentation of habitat through clearing and degradation of habitat from the effects of Phytophthora dieback, salinisation, intense bushfires and mining activities;
• Competition for nesting hollows with other hollow-nesting birds and feral honey bees;
• Illegal harvesting of nestlings for the cage-bird trade;
• Illegal shooting;
• Climate change;
• Stochastic events (e.g. disease, weather events);
• Vehicle collision.

As an example of the effect of a severe weather event, the local Carnaby’s population suffered a significant set-back when on 8 January 2010, the temperature reached 48^o C in Hopetoun and caused a massive mortality of cockatoos and other bird species on the central south coast. Deaths were reported locally from Hopetoun golf course, Jerdacuttup River and Munglinup. There were over 200 known cockatoo mortalities, but the total would have been much greater than this if it were to include unknown events. Prior to this event it was usual to record hundreds of cockatoos in Cocanarup during nesting surveys. Since 2010 the only cockatoos recorded there appear to be the nesting pairs.

It is also obvious to those who monitor nesting in Cocanarup that usurpation of nesting hollows by galahs, barn owls and feral bees is a detrimental factor in cockatoo breeding success.

Monitoring of nesting in Cocanarup

Monitoring of nesting in Cocanarup was initiated by the Friends of the Fitzgerald River National Park, when in October 2006 they organised an excursion to search for nests in the area. The twelve members who attended were reportedly delighted to find five active nests and many potential nest-hollows on that occasion. Until this time it seems that few people knew that it was a significant nesting area. The Forests Department made no reference to it in their management plan in 1980, and reports by biologists who have worked in the area make no reference to breeding until recently. The Friends’ excursion was probably part of a building momentum for the conservation of Carnaby’s as soon after this Birds Australia appointed a project officer to work along the south coast with community members to monitor Carnaby’s.

The Friends of Fitzgerald group is pictured in the image below around the historic Cocanarup spring located in the bed of the Phillips River, as it seems no excursion to Cocanarup is complete without learning something of the big story of the place. See: Narpulungup News Nov. 2006, #4, p.4.

Since 2007 when the first project officer started, monitoring has been carried out on a weekend in October each year and it is on-going. Consequently, over 10 years of data on nesting in this area has now been accumulated – and there is also now a group of dedicated people who are committed to continuing the effort and to protecting the Carnaby’s black-cockatoo.

See the next section (Significance of Cocanarup area for Carnaby’s) for a detailed summary of the latest (2019) nest survey.

Significance of Cocanarup area for Carnaby’s

The significance of the Cocanarup area for Carnaby’s black-cockatoo has been confirmed by BirdLife Australia, and communicated to the Federal Department of Environment and Energy, the WA Department of Mines, and relevant Ministers. Following are some excerpts from that correspondence (Dec. 2018):

“The Cocanarup area is one of the top three important breeding sites for Carnaby’s Black-Cockatoo in WA.”

“Presently there are 141 confirmed nest trees in the area, a further 35 potential nest trees (having suitable hollows but as yet no record of breeding), and each year up to 43 breeding pairs have been recorded breeding. These figures are an under-estimate because each year new nests are located and confirmed and due to the immense effort required to survey breeding, not all breeding events can be captured each year. It is estimated that closer to 60 breeding pairs breed in Cocanarup and the immediate surrounds. These breeding figures exceed those at most other sites within Carnaby’s breeding range that BirdLife is monitoring, further emphasising the conservation significance of the site.”

“Cocanarup is clearly a significant area for Carnaby’s during the breeding season and this is because of the high concentration of hollow bearing salmon gum trees across the reserve and the proximity of the area to extensive and undisturbed feeding habitat throughout the Ravensthorpe, Hopetoun and broader Fitzgerald Biosphere regions. The numbers of birds breeding at Cocanarup is typically not supported elsewhere (even where nests are present) because of the lack of food resources resultant of extensive clearing for agriculture across much of the birds breeding range.”

2021 nest survey outcomes

As in previous years, the Cocanarup Conservation Alliance (CCA) worked with staff from BirdLife Australia to organise and coordinate the annual survey of Carnaby’s black cockatoo nesting activity in and around the Cocanarup area, south-west of Ravensthorpe.

Survey Team at Work
Photo: Jarvis Smallman

Two periods of survey activity took place:

• Wednesday October 13th to Sunday October 17th, and
• Friday November 5th to Sunday November 7th

In total 15 local volunteers assisted at various times, with some involved for up to 5 days across the two periods:

• BirdLife staff provided 9 person-days in the field, and
• Volunteers contributed 36 person-days.

Outcomes are as follows:

• 309 large mature salmon gum trees were surveyed
• 253 trees were considered viable nest trees, and were logged in the BirdLife data system
• 59 trees had confirmed breeding activity (either live chicks, eggs, or both)

Trend / comparison with previous years:

• 2019: 179 viable trees surveyed, 70 with active nests
• 2020: 222 viable trees surveyed, 57 with active nests
• 2021: 253 viable trees surveyed, 59 with active nests

Summary: The survey effort this year increased and slightly more nests were found than last year but less than in the very productive 2019 season. This apparent decline in nesting activity might be of concern, especially as Cocanarup is considered the single most important natural nesting site for Carnaby’s (world-wide). It is thought this may be a consequence of a period of dry years reducing seed-set in the plants that the birds rely on – though it may also mark the ongoing decline of the species (thought to be +/- 10% p.a.).

Carnaby's eggs in salmon gum hollow
Photo: Jarvis Smallman

Carnaby’s Black-Cockatoo
Photo: Jarvis Smallman

On a more positive note, each year’s survey activity is increasing our knowledge and mapping of viable nest trees, which continues to enhance the importance of Cocanarup for the long-term survival of the species.

2020 nest survey results

As most members will know, the salmon gums of Cocanarup are monitored each year for nesting activity among the local Carnaby’s population. This is a collaboration between BirdLife WA and a group of local volunteers, and is now in its 14th year. This season’s survey was conducted over a series of days with the main effort occurring on the 16th – 18th October 2020.

Overall we found 57 active nests and, of the ones we were able to check with a camera, 9 had chicks, and 21 had 1 or 2 eggs. In total 222 trees were surveyed. Twelve of the active nest trees were new to our records. Last year we located 70 active nests from 179 trees surveyed.

The survey results suggest that breeding activity is down on last year and, while it is hard to pinpoint the reason for this, it is assumed that this year’s less than average rainfall, particularly through autumn and winter, would be an important factor in this outcome.

A monitoring team in Cocanarup checking the camera’s wi-fi monitor to interpret contents of the nest hollow above
Photo: Sue Leighton

Following our survey work done in mid-October, a Murdoch University team checked some of the nests 4 weeks later, in mid-November. This was preliminary to their proposed project to attach satellite-tracking devices to a limited number of birds. Unfortunately, in contrast to last year when Murdoch found chicks of above average weight, this year they found evidence that a number of known breeding attempts had failed. This was disappointing, and it reminds us how vulnerable the population is - and how critical good nesting habitat (and associated feeding and watering sites) is to the survival of the species.

The reasons for these apparently poor breeding outcomes can only be surmised because it is so difficult to closely monitor nesting and then to attribute cause to consequent observations.

The failure of actual breeding attempts may be due to shortage of food, given that this area has had 3 consecutive dry years and the bush has been distressingly dry with some plants dying and many not flowering and/or setting fruit for several years in a row.

Apart from causing a shortage of food for the cockatoos these dry conditions put pressure on all fauna and therefore there may have been an increased predation pressure on nests. Inclement weather during the breeding season might also have played a part, though it is hard to nominate with any certainty a particular event that would have been responsible. Beyond this, there may well be other factors involved which aren’t obvious to us.

Either way, in the short term this means that Murdoch University was unable to find enough suitable nest trees to proceed with the satellite-tracking program which they had planned for December. This too, is disappointing as we had keenly anticipated learning just where the birds were feeding during breeding and where they went once their offspring fledged. The Murdoch University team intend trying again next year, and we all hope for better outcomes then.

A patient female Carnaby’s waiting and watching while her nest is checked with the pole-mounted camera
Photo: Sue Leighton

CCA would like to acknowledge all those involved in this monitoring effort. This includes BirdLife WA staff (Vicki and Adam), 12 volunteers from the local area, 4 volunteers from Perth, and the Murdoch University team of 4 who travelled from Perth and spent several days down here. Volunteer hours totalled approximately 220 hours over 6 days, plus the Murdoch University effort. As everyone involved in monitoring at Cocanarup will attest, it is not easy country to work in, but it is a great way to spend a day (or more)! It is a wonderful salmon gum woodland, and the sight of a bird emerging from a hollow is more than ample reward. Sincere thanks to everyone who has been involved this season. It was a fantastic effort, one that does much to enable us to continue advocating for security of tenure for these entrancing and threatened birds.

2019 nest survey outcomes

Over five days in mid-October 2019 teams of local volunteers worked with staff from BirdLife Australia and DBCA to monitor the most recent Carnaby’s nesting season out in the Cocanarup salmon gums. This was a substantial effort by all involved and, satisfyingly, it produced the best set of figures recorded thus far.

The 2019 nest survey volunteers
Courtesy Sarah Comer, DBCA

Some of the key statistics were as follows:

• 179 trees were subject to a full tap-and-flush survey process, with many more tapped in hope as the team moved by;
• Of these, 143 were already in the BirdLife database, either as known trees from the past or as potential nest trees;
• 34 entirely new nest trees were located and added to the growing database;
• 62 trees were checked with the camera, which was fewer than hoped due to batteries failing along the way;
• Of these 62 camera-checked trees 38 were checked because females were flushed and the other 24 because they showed signs of active use;
• Of the 38 camera-checked hollows from which females were flushed 33 were confirmed to have either eggs or chicks or a combination there-of. These figures are important, as they indicate that over 80% of hollows from which females are flushed are likely to be active breeding attempts – which is useful when cameras are not available;
• There are now 199 trees which are known to have been used for nesting across the years, some of them repeatedly.
• Best of all, 72 females were flushed across the 5 days survey work – and of these it is thought just 3 may still have been “prospecting” for a nest site – which means there were 69 breeding pairs confirmed, a new record by far for Cocanarup.

While this is an impressive number, as is indicated by the comment below, it is also likely to be still a significant underestimate. There were likely to be many more breeding pairs because:

• Not all confirmed trees or areas were surveyed;
• Breeding was still in the early stages with most females sitting on eggs and pairs still prospecting;
• Listening surveys on the Sunday evening and ground explorations on the Monday morning indicated more breeding pairs in areas as yet never assessed.

In considering the outcomes of this work, BirdLife’s Vicki Stokes indicated that “Given what we’ve found this year, Cocanarup is quite likely the single most important entirely natural nesting site for Carnaby’s anywhere in the State (and therefore the world).” This underscores the critical importance of the rigorous process of survey work and data collection as these figures significantly enhance our efforts to have the wider Cocanarup area set aside as a Class A Reserve.