Feeding
Red-tailed Black-Cockatoos are specialist feeders, relying almost entirely on the seeds of Brown and Desert stringybark (Eucalyptus baxteri and E. arenacea) and Buloke trees (Allocasuarina leuhmannii).Clearing of these feed trees is considered to be the main threat to long-term survival of Red-tails. Unlike Yellow-tails which happily feed on seed from introduced plantation pines, Red-tails haven’t found an alternative food source. Management of remnant bushland also impacts on seed production. Too frequent burning of stringybark forest has been shown to contribute to reduced seed crops (Koch 2004). Stock grazing, particularly by cattle, results in ringbarking. This is mainly due to cattle rubbing up against the trunk. Eventually this leads to the tree dying.
Ringbarked stringybark Paul Koch, a biologist researching factors influencing food availability found that some food shortages are natural and due to Desert Stringybark fruiting on a three year cycle and Brown Stringybark on a 2-4 year cycle. Red-tails will feed on the species that has fruited most recently, preferring the softer seed capsule. Stringybark will retain the seed in the capsule on the tree, however as it matures, it hardens and requires more time and effort to extract the seed. This is critical for a nesting pair as it means the nest may be left for unusually long periods of time, resulting in nest failure. Effects of Fire on Food The amount of seed produced by stringybark trees is substantially reduced for up to 10 years following a fuel reduction burn or wildfire. In order to maximise the amount of seed available for Red-tails the Department of Sustainability and Environment will limit fuel reduction burning in stingybark forest within the range of the Red-tail. DSE is also investigating low intensity fuel reduction burning techniques to reduce the impact on stringybark seed production. Timing fuel reduction burns to avoid years in which stringybark forests are carrying heavy crops of newly matured seed capsules will also help to minimize the impact of fire on Red-tail feed trees.
Remnant buloke is mostly restricted to roadside remnants or scattered paddock trees
Buloke occurs on heavier, more fertile soils favoured for agriculture]. Only about 2% of buloke remains across the Red-tails range. The birds move to Buloke areas in late summer and autumn to feed on the seeds. Unlike stringybark, buloke does not retain the seed in the capsule.
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Red-tails leave a tell-tale litter of twigs and chewed capsules (“chewings”) beneath their feed trees
Scattered paddock trees
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