Yellow-tailed Black-Cockatoos have a diverse diet. They feed mainly on the seeds of native plants particularly in the Proteaceae family (Banksia, Hakea), while larvae of wood-boring insects (in Acacia, Casuarina) can make up a significant portion of the diet; making the Yellow-tailed Black Cockatoo unique amongst parrot species in south-eastern Australia as they can be thought of as an omnivorous cockatoo.

Buds, flowers, sap and galls have all been reported as being consumed by this species.

Nectar and/or flowers are commonly eaten. The flowers of Banksia integrifolia (seasonal) and Lambertia formosa (Mountain Devil) appear to be a favoured choice.

These plant species occur in the habitats that YTBC will be frequenting to feed on their staples of Banksia and Hakea etc, i.e. in coastal heath and banksia woodland. It may be opportunistic that they then include flowers while feeding on seeds and larvae in the area.

Yellow-tailed Black-Cockatoos consume the rich nectar of Lambertia formosa by either squeezing the base of the flower, or tipping the flower up into the beak with their head back, in what could only be described as a drinking action.

They seek out the seeds from pine cones of the introduced Pinus radiata. An observation and lab study in the late 1980s confirmed the species extracted fungi and slime mould from under the bark of dead trees (1). These exceptionally intelligent birds know exactly where, when and how to find the food they want, and there is still a lot to learn about them.

Juvenile Yellow-tailed Black Cockatoos of a certain age will alternate between staying still and begging – often for long periods of time – and experimenting with self feeding such as holding Banksia fruit to (often clumsily) try and extract seed; usually while still vocalising to the nearby parents until he or she then reverts back to full begging mode and is fed by one of the parents through regurgitation of food from the crop.

Banksia

The evolution of YTBC is clearly closely intertwined with the Banksia genus, and the wider Proteaceae family. Their powerful, slender, long bills – much more narrow than that of the two other eastern Australian black-cockatoos – provides the perfect tool for breaking into hard Banksia infructescences and precisely extracting the small seed from within the narrow follicle. Maybe even more so though, is the adaptation of a slender bill to pulling out grubs deep within branches and trunks.

While the Red-tailed Black-Cockatoo shares much of a similar diet to YTBC in parts of their range, their beaks are noticeably wider than than of YTBC.

Unlike Glossy Black-Cockatoos whose extremely wide beaks have evolved specifically to feed on Allocasuarina seeds, the bill of YTBC is not “designed” to feed on one type of food, but provides the perfect tool for everything from Banksias and Hakeas, and introduced pine cones, to tearing deep into hard wood for larvae. Across the much wider range across the continent of the distribution of Red-tailed Black-Cockatoos, the different subspecies have evolved slightly different bill sizes according to food availability.

But perhaps above all else, it is the Banksia that is the most important plant genus to Yellow-tailed Black-Cockatoos. The distribution range of the genus in eastern Australia is correspondent to that of the birds’ distribution range. Human occupation of the coast has resulted in extensive, widespread and continual clearing and degradation of Banksia and other YTBC habitat.

YTBC are adept at locating standalone individual Banksia trees planted in suburban gardens, to which they will often return annually.

Most Banksia species in the south east provide a year-round food source for Yellow-tailed Black-Cockatoos, as their seed-containing follicles mostly remain closed for long periods of time, until fire or death of part of all of the plant stimulates the opening of the follicles and release of the seeds.

One exception to this is Banksia integrifolia (coast banksia) which does not hold on to its seed. When the seed is mature the follicles soon open for seed release, with no seed being held on this plant at the end of each season. This occurs in the late spring into early to mid-summer. Yellow-tailed Black-Cockatoos have an obvious instinctive pattern of behaviour to descend on coastal areas in flocks during this time specifically to access the seeds of B.integrifolia, although they will also consume some other foods while in the area (e.g. larvae). However, B.integrifolia is clearly their primary and specific purpose for moving to specific locations along the coast for this short window of time every year. Some pairs will have dependent young at this time, who can often be seen experimenting with how to eat Banksia seeds. Some years I have noted them arriving earlier in the season and consuming the flowers of B.integrifolia.

Once the concentration of B.integrifolia seed pods have diminished to the point where there’s not enough to sustain the flock or warrant their effort, the number of birds reduces and flocks eventually move on.

This is a widespread species in eastern Australia occuring in many different habitat types, so the diet varies as to what is available in any particular location or habitat. But regardless of where they are, the Yellow-tailed Black Cockatoo seeks out specific types of inverterbrates in the form of wood-boring larvae. At times it’s possible that these larvae are not just a supplement to the diet, but could be a dominant part of the diet. This species has a beak shape that has evolved to carry out to this very task in a methodical and expert manner.(2)


References
1. Fungal feeding by Yellow-tailed Black-Cockatoo
2. Cockatoos, Matt Cameron CSIRO Publishing 2007