Forest Red-tailed Black Cockatoos & their Urban Ecology

Erika Roper treated a packed house to a well-illustrated, informative and entertaining talk on her study of Forest Red-tailed Black Cockatoos, work she is conducting for the degree of PhD at UWA. Much of the talk was focused on the spread of these cockatoos into Perth’s urban environments, where they have been able to exploit the exotic—but widely planted—Cape Lilac (Melia azedarach), freeing them from a restricted diet of (mostly) Jarrah and Marri seed, which constitute their staple diet in their natural forest habitat. Such local trees are now largely absent from the urban sprawl on the Swan Coastal Plain.

Male Forest Red-tailed Black Cockatoo
Male Forest Red-tailed Black Cockatoo
(E. Roper)

Before Erika introduced the issue of diets, she gave us some basic information on topics including:

  • What are Black Cockatoos? (There are five species in Australia, three of them in the South West.)
  • How to distinguish the Forest Red-tailed sexes and tell adults from immature birds; for example, the males have a dark beak, the females a pale one. The male has solid red tail panels, the female’s tail is striped with yellow, orange, or red bars; the juveniles look more like a female.
  • The composition of family units.
  • An overview of the factors that can drive immigration to novel, or/and emigration from, traditional habitats
  • A chronological history of this cockatoo’s shift from the forests. (Prior to 2000 there were few records from the coastal plain; the most dramatic increase in numbers has occurred particularly since 2010). This was illustrated with clear maps of the records in different time periods.

Besides diet, one fascinating aspect of these cockatoos’ adaptation to urban life is a shift in call pitch. In urban areas where there is much confusing, low-frequency traffic noise, the birds tend to cut out the low frequency component of the calls that get drowned out by traffic noise, but retain the higher frequency components. Yet they continue to use the low frequencies in the forest. Erika emphasised that this was still a preliminary finding.

Erika summarised her conclusions so far:

Erica with cockatoo
  • 1. The driving force behind the expansion into urban areas seems to be exploitation of a novel food source, not habitat loss.
  • 2. Cape Lilac is a faster, more efficient, and predictable food for cockatoos than native foods (although, in question time, she said its nutritional values are still unknown and others pointed out it is a weed tree).
  • 3. Urban cockatoos prefer food trees that are closer to bushland and green space.
  • 4. Urban cockatoos appear to be adapting their calls to urban areas.
  • 5. Long-term impacts o f urban food and life are (as yet) unknown.

A particularly pleasing aspect of Erika’s talk was her approach, which emphasised aspects of the natural history of the Forest Red-tailed Black Cockatoo, and their implication for understanding and managing this threatened species. It was refreshing to see that all-important natural history had not been over-shadowed by statistics and sophisticated technology.

Dr Tony Start

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