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What’s under the Skirt? Dead Washingtonia leaves as habitat for birds and bats.

Cultivated in Australia since the 1880s, the two North American fan palm species, the Californian Fan Palm (Washingtonia filifera) and the Mexican Fan palm (Washingtonia robusta) are a common sight in many Australian communities. The palms go under various colloquial names. W. filifera is known as ‘sky-duster palms,’ ‘’railway palms,’ ‘desert fan palm,’ ‘American cotton palm,’ ‘petticoat palm’ (because of the ‘skirt’ of dead leaves that cover the stem) and while W. robusta is known as ‘Washington palm,’ ‘Mexican washingtonia,’ ‘Cotton Palm’ and also ‘sky dusters.

As these palms were widely marketed by the horticultural trade they now have a global distribution. A systematic review of the ecological provisioning services provided by these palms has shown that their drupes (fruit) are consumed by a wide range of birds, fruit-bats and terrestrial animals. While coyotes are the main disperser of seed in the palms’ original distribution range of Southern California and northern Mexico, many native species in other countries have adapted to feed on the fruit offered by these exotic palms.

Little is known about the animals that feed on the palm fruits here in Australia. On record are only Pied Currawong, Starlings and Blackbirds, as well as fruit bats, but there are bound to be many more bird species that eat the fruit.

Even less is known about what goes on under the ‘skirt’, the array of dead leaves at the bottom of the crown of both species. These dead leaves persist in particular among W. filifera as well as the hybrid Washingtonia X filifera, unless they are arboriculturally removed for aesthetic reasons or because they pose a fire risk. In the southern USA, a wide range of birds (among them sparrows, owls and parakeets), small bats as well as rats use these leaf thickets as nesting and roosting habitat. In Europe, feral parakeets and rats have likewise colonised these spaces.

In Australia nothing is known about what goes on under the ‘skirt’ of our palms, despite the palms being so wide spread. Arboriculturalists are uniquely placed to assist, as they are regularly engaged in the pruning and tidying up of these palms. Many will have noted wildlife or evidence of its activities, but not thought it worthwhile to photograph or record it.

We would like to hear from you. Next time you are pruning, or removing, Washingtonia, look under the skirt and tell us what you find.

For more information and to assists with this research please contact A/Prof Dirk HR Spennemann, Institute for Land, Water and Society; Charles Sturt University; PO Box 789; Albury NSW 2640 or via email at dspennemann@csu.edu.au

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