Hollows old and new

Hollows old and new | Tuesday, 17 January 2023

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Hollows old and new

Providing options for breeding Carnaby’s Black-Cockatoos

Two of our initiatives — to repair and refurbish artificial nesting hollows that were installed years ago, and also to set up new ones — have provided breeding opportunities that Endangered Carnaby’s Black-Cockatoos need so desperately, combatting a shortage of natural hollows in key parts of the species’ range across parts of Western Australia.

Repairing and renovating old artificial hollows

While there is currently a big focus on installing new artificial hollows for black-cockatoos to aid their breeding, the maintenance and repair of existing artificial hollows is commonly overlooked. Nevertheless, maintenance of old hollows is essential to ensure that they remain viable breeding options for Carnaby’s Black-Cockatoos. If they fall into disrepair, they may actually become dangerous for cockies trying to breed in them. The focus of this intervention was the Newdegate region in Western Australia’s Wheatbelt.

The refurbishment of black-cockatoo hollows involves a number of key factors:

  • One of the most important tasks is topping up the layer of woodchips which accumulate at the bottom of the hollow. Over time, they break down and become compacted, affecting nest drainage and access. In 2022, more than 1500 litres of wood chips were used to top up 30 artificial hollows around Newdegate.
  • The replacement of ‘sacrificial’ chewing posts attached to the inside entrance of each hollow is another crucial factor. The birds habitually chew on these bits of wood, contributing to the layer of wood chips in the hollow. If the chewing post gets eaten away, the cockies may then chew the base of the hollow, creating holes which eggs or chicks can fall through.
  • Ladder maintenance is also important. A small ladder installed in each nest allows the birds to climb in and out of their artificial hollow, and our work ensures they are secure, providing safe climbing conditions for both nesting and fledging black-cockatoos.

Installing new artificial hollows

In just its second year, ‘Adopt a Cocky Nest’ has already seen success, with ever increasing numbers of artificial nest hollows being used by Carnaby’s Black-Cockatoos.

The scheme began in 2021 to install artificial hollows in known breeding locations. Our initial aim was to install 24 hollows on private properties across the Bullsbrook, Bindoon and Chittering regions — all well-known Carnaby’s breeding locations — for the cockies to nest in, but instead we raised sufficient funds to meet our initial target, plus an extra 15 hollows.

Back in 2021, just a few months after the artificial nests were installed, we confirmed that five of them were being used for Carnaby’s breeding, with either one or two eggs in each of the active hollows. Several Carnaby’s were also found breeding in natural hollows, either in the same trees as artificial hollows or in trees nearby.

This breeding season — just our second — saw additional birds nesting in the hollows.

This time we observed six of our hollows being used by breeding Carnaby’s Black-Cockatoos: one contained a single egg; another two had two eggs (and there was a 7-week-old chick found in a natural hollow in the same tree as one of them); two had an egg and a chick; and one had a single 5-week-old chick.

Hopefully, over time, the Carnaby’s will continue to discover the artificial hollows and make use of them — sometimes hollows can remain unused for up to 10 years before Carnaby’s breed in them for the first time!

Providing new hollows and repairing old ones provide an essential component (among a range of conservation actions) in our overall strategy to drive the recovery of Carnaby’s Black-Cockatoo populations (and those of other threatened black-cockatoos) in Western Australia.