Carb-loading Ibis are long-term stayers
creative commons
We know that Australian White Ibis enjoy a sandwich in the park, but it's not just because sausages aren't on offer.
An investigation of the dietary preferences of urban Ibis reveals that they actively select carbohydrate-rich food, rather than the proteins that make up their natural diet.
Carbohydrate-loading is normally a strategy used by athletes to improve their long-distance performance. Like marathon runners, Australian White Ibis frequently travel long distances, even in cities, where we have tracked them flying 30 km to rich feeding sites to obtain food to provide to their young. However, some park-frequenting birds hardly move away from their nest-tree, bathing fountain and favourite rubbish bin.
In our monthly surveys of colour-banded birds, several of our friends were sighted on more than 60 occasions in north Hyde Park without venturing across William St, while other birds were confined to south Hyde Park. Clearly these birds have no big need for carb-loading, and our observations of them chowing down bread, rice and pasta, might simply be a consequence of the food that people leave around.
But our latest research, led by Sean Coogan, a PhD student at the University of Sydney, has shown that Ibis actively select carbohydrates. When presented with a smorgasbord of three types of similar-looking pellets, they consumed significantly more carbohydrate-rich pellets than the high-protein and high-fat options. It seems that their foraging choice is for particular macro-nutrients, rather than simply seeking energy.
Ibis in their traditional wetland homes have high protein diets, feeding on insects, crustaceans and frogs. Even in the city they spend much of their time feeing on natural foods, with worms being a particular favourite after rain. Why they should select carbs we don’t know, but it might be because, like us, they actively seek out foods that might have been relatively scarce in their ancestral diets.
What we do know is that Ibis are now thriving in our cities and with a reduction in inland wetland flooding they are here to stay. It pays to understand your neighbours, and I’m pleased that like their ancient Egyptian sisters, the Australian White Ibis (a.k.a. Bin Chicken) is now taking on cult status – see the clip below.
Richard Major, Principal Research Scientist, AMRI
More information:
- Coogan, S.C.P., Machovsky-Capuska, G.E., Senior, A.M., Martin, J.M., Major, R.E. & Raubenheim, D. (2017) Macronutrient selection of free-ranging urban Australian white ibis (Threskiornis moluccus). Behavioral Ecology, doi:10.1093/beheco/arx060.
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