At this time of year, I see two different types of large parrots everyday. The Yellow-tailed Black-cockatoo (above) and the Sulphur-crested Cockatoo (below). One of them eagerly gobbles down the bird seed offered by some of my neighbours. The other never visits the feeding trays. Why should this be?

Yes it’s the Sulphur-crested Cockatoo that visits the seed trays. They also fly off to forage elsewhere…  often on the ground, where they dig up bulbs and eat cereal crops. While the Yellow-tailed Black-Cockatoo feeds on wood-boring grubs, the seeds and flowers of the native Banksia trees, and the seeds of the introduced pine trees (Pinus).

But why wouldn’t the Yellow-tails treat themselves to a free feed now and then? They seem pretty tame…

I did some reading and found some interesting features of cockatoo beaks described by Homberger (2003), but no description of the Yellow-tailed Black-Cockatoo beak. I really wanted to look at these beaks myself, so off I went to the Queensland Museum, to check out their cockatoo skull collection. At the start, my plan was mostly to draw the skulls for an art project. Bird and mammal collection manager Heather Janetzki was wonderfully helpful, and had a bunch of specimens ready when I arrived.

The collection included good skull specimens of eight different cockatoo species. By ‘good’ I mean those with the keratin part of the beak tips still attached, and with a separate jaw (mandible) that matched the skull. Once I started looking at these specimens, I realised there were many fascinating differences and similarities between the species that related to their diets. Surely this information had been documented before? I needed to do more reading… But after weeks of looking, drawing, and reading the scientific literature… it turns out that these relationships between cocky beak structure, function, and diets hadn’t been documented in any detailed and systematic way.

After a 25-year break from pure ecological research, I suddenly found myself completely immersed in a fascinating scientific project. It felt good 🙂

There are so many stories to tell! But I’m starting here with these two cockies:

Can you see any differences in the skulls of these two species? (below) A. Yellow-tailed Black-Cockatoo Zanda funereus; B. Sulphur-crested Cockatoo Cacatua galerita. Note that the keratin part of the Sulphur-crested Cockatoo specimen only covers the beak tips, and the rest of it is missing,

And below are the same specimens, but this time drawn from the front. Yellow-tailed Black-Cockatoo Zanda funereus A. front view of skull, B. Front view of mandible (jaw); C. Sulphur-crested Cockatoo Cacatua galerita, front view of skull, D. front view of mandible. Drawn from Queensland Museum specimens.

Can you see the different shapes of the upper and lower beak tips?

Also, and importantly, the Sulphur-crested Cockatoo has a ridge or ‘step’ on the inside of its upper beak. It also has finer and shallower horizontal ridges (lamellae) between this ‘step’ and the tip of its upper beak. See my notes below:

It seems that the tip of the lower beak can press food against the ‘step’ inside the upper beak, and this is probably quite an efficient way to dehusk and/or crush small seeds. See image below, partly redrawn from Homberger (2003).

The beak tips of the Yellow-tailed Black-Cockatoo are shaped like the tips of pincers. The ends are quite sharp. But there is no ‘step’ on the inside of the upper beak, and no lamellae. This beak can prise open the wood of branches to get at wood-boring grubs. It can also prise open banksia and pine cones to get at the seeds.

These birds crush banksia seeds between their beak tips – or maybe just remove the parts they don’t want (banksia seeds have a small ‘wing’). I think these birds might be able to dehusk small seeds too, using their beak tips. But it would be an extremely time-consuming and frustrating task, as the bird would probably drop more seeds than it ended up processing. Even if it takes some time to extract a big fat juicy grub out of a branch…. that big fat juicy grub is probably far more satisfying than a few stale sunflower seeds.

Three months ago I made a cartoon about the amazing cocky beak. It led me to ask more questions, which led me to the Queensland Museum, and now I’m preparing three scientific papers.

There are many more stories to tell about parrot beaks, but they will have to wait for another day.

Thanks for reading this and supporting my work. I feel very fortunate that I have the time and opportunity to pursue science as a hobby, and as a volunteer. And your support helps me do this.

Reference:

Homberger, D. G. (2003). The comparative biomechanics of a prey-predator relationship: the adaptive morphologies of the feeding apparatus of Australian Black-Cockatoos and their foods as a basis for the reconstruction of the evolutionary history of the Psittaciformes. Vertebrate biomechanics and evolution, 203-228.