Most nature enthusiasts in the region are familiar with the white-throated treecreeper, a small to medium-sized brown bird that lives up to its name by creeping up trees on the bark, its white throat catching in the forest light. These birds call loudly and persistently, with a number of different calls, but all with the same strident, far carrying quality. I see or hear these plucky little birds nearly every time I am walking in the bush.
Much more difficult to see and hear is the smaller red-browed treecreeper, also found in the Wombat Forest. Red-browed treecreeper calls are described by Graham Pizzey as a “distinctive quick explosive, zizzing chatter”. However, unlike the loud call of the white-throated, this species is mostly silent – moving quickly over the tree bark, stopping to investigate hanging bark and the bark around knot holes and hollows.
How is it that these two similar species can live together in the Wombat Forest without stepping upon one another’s toes ecologically, so to speak? The most detailed studies that compare the white-throated and red-browed treecreeper were undertaken in NSW in the 1980s by Richard Noske, who carefully recorded where the birds foraged, what trees they preferred and other similarities or differences in their behaviour.
Noske found while the white-throated spent most of its time travelling up tree trunks and large branches, the red-browed spent a lot of foraging time travelling along smaller branches, and investigating bark strips and hollows as I mentioned earlier. The white-throated is happy with any kind of bark trees, but seemed to prefer peppermints and stringybarks. Whereas the red-browed prefers trees such as manna gums with the hanging bark, especially in the branch-trunk creases. The white-throated may be found throughout the forest, but the red-browed seems to prefer gullies. This may be the case because gullies are where gums such as Manna gum prefer to grow, and often many larger trees remain in gullies whereas they lost on the slopes and ridges.
So, these birds have some effective resource partitioning going on – they each have a niche that provides their food of insects, spiders and other invertebrates.
Why is the white-throated Treecreeper so common and the red-browed Treecreeper much less so? Detectability is a factor. You can tell if a forest patch contains white-throated very quickly due to their loud calls. I have only seen red-browed treecreepers when I have binoculars and looking specifically for birds. Availability of suitable habitat is definitely key, as these birds prefer large old gums with lots of hanging bark and creek and river gullies which are only in some areas of the Wombat Forest.
The red-browed treecreeper does not occur at Mt Cole or at the Otways, so here in the Wombat we are seeing the species at the western point extremity of its range which follows the Great Dividing Range all the way to the Queensland/NSW border forests.
The red-browed treecreeper is a co-operative breeder; young from previous broods stay with the parents and help raise the next young. Red-broweds have much larger territories than the white-throated treecreeper, and a slow breeding rate. They rely on small to medium-sized hollows completely for breeding, and are vulnerable to disturbances from logging, wildfire and loss of hollow bearing trees in prescribed burning operations.
Let’s hope this handsome little bird continues to persist in the Wombat Forest for many years to come, despite being a bit tricky to see, much like the dear little eastern pygmy possum featured last month.
My next article will be on the koala. I am excited to announce Janine Duffy – director of the Koala Clancy Foundation and koala behaviour expert extraordinaire – is coming to Daylesford. She has been studying the koala population of the You Yangs for more than 20 years and pioneered the use of nose pattern recognition as a way to recognise individual koalas. Sunday June 4, Daylesford Neighbourhood House, 3.30pm. Please RSVP to Margie Thomas on 5324 2112.