Late winter, and the birds are loudly squabbling. Defending nesting hollows, and carrying nesting material. It is always surprising that this behaviour begins when it is still cold, especially this year.
Many native species of birds and mammals are dependent on tree hollows, as shelter, for protection, breeding and socialising. In NSW alone, 81 bird species are reliant on tree hollows for shelter and nests.
Tree hollows are only found in "old growth" forests and trees and these are the trees that have been systematically removed from the landscape, primarily for housing development, farming and for timber.
Removal of hollow-bearing trees may lead to displacement and death of a bird species using the hollows locally, a threat to biodiversity.
Hollows used by birds are not selected at random. Each species has its own requirements in terms of hollow size, location (branch or trunk), tree species and surrounding vegetation.
Some birds prefer to use hollows in old dead trees.
I was fascinated recently, at Earthcare Park in Tenambit, to watch the meticulous inspection of a series of hollows by a pair of corellas, at the same time actively defending the hollow from invading lorikeets.
Hollows take decades to form and not all trees form hollows. They are created after storm damage, by termite and fungal activity and by some birds "renovating', by chewing out the wood to an acceptable shape and size.
It takes about 120 years for a small hollow, suitable for small parrots to form, 220 years for a medium sized hollow and 300 years for a hollow big enough for a kookaburra or cockatoo to inhabit. Many birds will be extinct locally before trees planted today are big enough for them to use as nest sites.
Some of the birds that use hollows are, the Australian Owlet-nightjar, Treecreepers, Tree Martins, all cockatoos, most parrots, kookaburras, some birds of prey, dollarbirds and the Australian Wood Duck. I am always surprised by ducks in trees!
What can we do to help prevent extinction? Most importantly protect old trees, even dead ones and plant new trees wherever possible, that will form hollows (Eucalypts usually).
Install nest boxes in areas where old trees are missing. Not all birds will use nest boxes but for the love of our birdlife, it is worth a try.
Hunter Bird Observer's Club website can be found at: http://www.hboc.org.au/ or follow us on Facebook.