The lovely folks over at Birdlife Western Australia recently asked me to write a short article to contribute to the Summer 2018/19 edition of Cocky Notes. Cocky Notes is a bi-yearly newsletter filled with all things cockatoo in south-western Western Australia. As all three species of Black-cockatoo in WA are threatened Birdlife has several ongoing projects focusing on helping the cockies, and the newsletter is a way to update everyone on their progress. There are also researchers like myself working on the Black-cockatoos, and we sometimes contribute to the newsletter to provide updates about our research.
A large flock of Red-tailed Black-cockatoos resting at an urban roost site in Shenton Park, a suburb of Perth, WA.
This edition of Cocky Notes has several interesting articles, including a recap of the first National Black-Cockatoo Forum (held in Melbourne in November 2018, which I’ve been meaning to write about myself!), an update on Birdlife’s new CockyWatch citizen science program, and info on last year’s Carnaby’s Black-cockatoo breeding surveys.
You can download the Summer 2018/19 edition of Cocky Notes here. I’ll add my article below in case you are unable to download the full issue right now. You can find past issues here.
FAST FOOD FOR COCKATOOS
Do you know what Red-tailed Black-Cockatoos eat? Seeds. Unlike Carnaby’s and Baudin’s which also feed on flowers, nectar and grubs, Red-tailed Black-cockatoos feed almost exclusively on seeds. In the Jarrah forest, where Red-tails traditionally live, their diet consists mainly of Marri and Jarrah seeds, supplemented with a few other seeds when available.
Around the year 2000, some Forest Red-tails were first observed in urban Perth on the Swan Coastal Plain. While it is likely that a search for water during the drought triggered the move, it was food that made them stay. Urban areas are filled with a multitude of tree species, both native and exotic, that are planted in parks, gardens and on street verges, any of which could be a potential food resource to an ingenious cockatoo. The urban Red-tails have learned to exploit these new food resources and are thriving in Perth.
Numbers of Red-tails seen in urban areas have drastically increased over the past few years as more and more individuals and family groups learn about the resources available in the city. One of the main urban food resources on the Plain for the Red-tails are the seeds of the Cape Lilac tree. Every year when the Cape Lilac trees produce fruit, flocks of Red-tails descend on the trees and strip them bare, leaving a mess in their wake.
This is not to say that the cockatoos had to move to the city for food. Natural food is abundant in the Jarrah Forest — there are Marri and Jarrah nuts galore! The cockatoos just appear to like city food better, especially Cape Lilac.
Cape Lilac provides a predictable food supply that is available for most of the year (Jan-Oct). However, the recent increase in urban Red-tail numbers has altered the availability of the Cape Lilac seed. Today, most of the Cape Lilac is consumed by winter and the Red-tails must return to the forest to feed. When compared to traditional foods like Marri, Cape Lilac is also much faster and more efficient for the Red-tails to eat. In the time it takes for a cockatoo to process a marri nut and eat the seeds, it could have eaten 25 Cape Lilac seeds!
It is also highly likely that Cape Lilac is much higher in energy than their traditional foods, as the seeds are very oily. However, the impacts of feeding on Cape Lilac on birds’ body condition, health and breeding potential is presently unknown and it is always best for birds to feed on a varied diet of primarily native food plants. This research is still underway, so stay tuned for the results! You can keep up-to-date by following me on Twitter @_erikaroper, on Facebook, or at my blog.
A family unit of red-tailed black-cockatoos feeding in a cape lilac tree in Coolbellup, a suburb of Perth, WA.