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Birds

Hollow Promise.

Bramanda are fortunate enough to live quite close to a park that has an appreciable number of tall, old trees. And for a park of its size, it has a surprising number of hollows in those trees, making it a very important local ecological area.
On a weekend towards the end of winter, the local birds were all beginning to make their inspections for the upcoming breeding season.

A Rainbow Lorikeet:

According to the Wilderness Society, 303 Australian native species are dependent on tree hollows for survival. That includes 114 native bird species – that’s 15% of all native bird species.

Not long after the Rainbow Lorikeet had finished his inspection, these two lovers showed up:

These Sulphur-crested Cockatoos (Cacatua galerita) began to take an interest in the same hollow. We couldn’t help thinking this one would have been a bit too cosy for them.

Timber-felling and clearing land for agriculture places enormous pressure on hollow-dependent birdlife. The terrible bushfires of the summer of 2019/2020 have added to the loss of old hollows.
Even the best reforestation programs are of little help: some studies suggest that it takes 70 years for natural hollows to form in many native trees. The Mountain Ash can take 120 years. A study from Charles Sturt University says that it can take anywhere between 200 and 400 years for a hollow to form that is large enough for some owl species.

Higher up on the same tree as the Rainbow and the Sulphur-cresteds, this Galah (Eolophus roseicapilla) was showing some interest in a hollow with a handy landing ledge. Because he was alone and was making such a noise and display, we conjectured it may have been a case of finding a hollow first, and trying to attract a mate afterwards!

There are seven non-native, invasive bird species in Australia that also nest in hollows. Chief amongst them is the Common Myna (Acridotheres tristis) – which will also use hollows in rocks or walls. The prevalence of these birds is further competition for a decreasing number of hollows. In our park, however, these were the only ones we could see in a hollow.

But competition is enough that birds like this Sulphur-crested Cockatoo have to consider all possibilities – even the top of this rotten telegraph pole, which would be totally exposed to the elements.

Another Rainbow:

The Sulphur-crested Cockatoo eventually tried out a more reasonable sized hollow. He seemed happier with this one.

There are many movements afoot to try to help overcome the problems of hollow scarcity. Nest Box Tales (https://nestboxtales.com/) is a community group that supplies plans and sound advice about building and positioning nesting boxes for a large range of native birds and other fauna.

Researchers at the Charles Sturt University have been 3D-printing plastic nest boxes, double-walled for insulation, with designs that can be tailored to fit particular trees, and have a greater longevity than wooden boxes.

Hollowhog is a newly-developed tool for carving out cavities in living trees that purports to cause less damage than previous methods. It’s probably too early to tell how successful this will be.

But in our local park, at least, there seems to still be a lot of comfortable hollows around for birds of all sizes. Like the Sulphur-crested above, this guy backed himself into a spacious cleft, and settled down contentedly.

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