Monday, 26 May 2008

Orange-footed renovators

The mounds are to be met with here and there in dense thickets, and are great puzzles to strangers, who cannot understand who can possibly have heaped together cartloads of rubbish in such out-of-the-way places; and when they inquire of the natives they are but little wiser, for it almost always appears to them the wildest romance that it is all done by birds.
Alfred Russel Wallace, 1869
'Bali and Lombok' in The Malay Archipelago

Bushy Creek runs along the boundary of Kingfisher Park. A rustic bench overlooks the water. You can sit here for hours watching the birds as they drop by to forage and bathe. I shared a lot of time at the creek with spectacled and pied monarchs, rufous fantails, little shrike-thrushes and even an azure kingfisher. (Duncan at Ben Cruachan Blog has a photo of one of these dazzling creatures, which I'm convinced are the product of an alchemist who can turn gemstones into birds.)

Orange-footed scrubfowl have built a nest in the rainforest along the creek. Nest is perhaps an understatement. It's an edifice, a massive mound of leaves and soil raked up from the forest floor. So big is this structure that scrubfowl make brush turkeys look like slackers.
  • Scrubfowl mound: up to 5 m high and 12 m in diameter
  • Brush turkey mound: up to 2 m high and 5 m in diameter
See? No wonder turkeys have made a pastime out of mooching. They've got all that spare time to fill.

Evidence of a turkey filling its spare time with mooching

Scrubfowl construct their mounds in closed forest. Occasionally, abandoned mounds are found in woodland or savanna, indicating that vegetation type has changed at some time. Inferring a change from the nests is one thing, pinpointing the time is quite another. Radiocarbon dating gives unreliable results because scrubfowl constantly bring in, chuck out and rework the material in their mounds. They are the ultimate renovators.

(For a video of scrubfowl in action, click here. 2.6 MB)

Bright orange feet are a requirement of OH&S regulations


ETA: Those figures for the maximum dimensions of a scrubfowl mound came from Pizzey's Birds of Australia, which is pretty good on these sorts of things. But I've just been searching for more information on the subject. I haven't been searching very hard, of course. If anything requires more effort than a few keystrokes, you can forget about it. The less-than-authoritative internet gives figures from 4.5 to 7 m in height. This reminds me of the changing dimensions of the giant squid.