Monday, 10 July 2006

Your feets too big

Australia has three species of megapodes. Megapodes are large birds that build nests from mounds of leaves, which they rake up with their large feet. (Mega-podes—geddit?) Rotting vegetation warms the eggs inside the mound. If it's too warm, the birds scratch away some of the leaves. If it's too cool, they pile on more.

Unless you make a big effort, you're unlikely to see the rare and secretive mallee fowl (Leiopoa ocellatus) of the southern mallee. Orange-footed scrub fowl (Megapodius reinwardti) are easier to spot in the rainforests in the Northern Territory and Wet Tropics. Still, they can be a little shy. But you can hardly miss the brush-turkeys (Alectura lathami). They hang around picnic tables along the East coast, waiting for unwary tourists to sit down and unpack the sandwiches. Then they mug the poor saps.

A brush-turkey is an odd-looking bird. The tail folds vertically, which is strange enough. The featherless head and neck are scarlet. The chrome yellow wattles around the base of the neck look like a deflated balloon. To top it off, there's a sprinkle of black fluff on the top of the head.

But don't let the whimsical appearance fool you. They're as cunning as outhouse rats. Among their little tricks is a neat scam where one decoys the gullible by playing the fool while the others raid the hamper, Yogi Bear-style. I speak from experience.

Don't feed the turkeys. Populations increase rapidly in spots where they get regular hand outs. Areas with high densities of not-so-dense turkeys lose leaf litter, seedlings and ground cover. The birds move through the scrub like bulldozers, scraping away the surface covering and ripping out plants as they go.

Turkey nests are about 4 m across and up to 2 m high. The sex of the hatchlings depends on the temperature inside the mound. At optimum temperature (which the male tries to maintain), the sex ratio is 1:1. If it's cooler than that, the hatchlings are male; if warmer, they're female. But this isn't the same mechanism that controls reptile sex determination. Instead, skewed sex ratios result from embryo mortality at different temperatures.

Chicks are superprecocial. After they crack open the egg with their big feet, they take up to 55 hours to escape the mound. They feed, preen and snooze in between bouts of scraping their way to the top. Once at the surface, they disperse, never receiving parental care. Emerging chicks have well-developed wing feathers. They can't sustain flight for very long but they are capable of short bursts.

With all these things going for them, it's hardly a surprise they're taking over in Queensland. I, for one, am getting ready to salute my avian overlords.

Read more

Göth, A. (2002). Behaviour of the Australian brush-turkey (Alectura lathami, Galliformes: Megapodiidae) chicks following underground hatching. Journal für Ornithologie 143(4): 477–488.

Göth, A. (2005). Temperature-dependent sex ratio in a bird. Biology Letters 1: 31–33.

Starck, J.M. & Sutter, E. (2000). Patterns of growth and heterochrony in moundbuilders (Megapodiidae) and fowl (Phasianidae). Journal of Avian Biology31: 527–547.

Warnken, J., Hodgkinson, S., Wild, C. & Jones, D. (2004). The localized environmental degradation of protected areas adjacent to bird feeding stations: a case study of the Australian brush-turkey Alectura lathami. Journal of Environmental Management 70: 109–118.


David Nelson said...

Nice info Snail. I'll add a bit of local knowledge from Chatswood in North Shore of Sydney. Sometime in the last five years or so these guys turned up in our bushland and adjacent leafy suburbs. Notable because this now marks the southernmost limit of the species' range. Their appearance has been attributed to the fox-baiting that's been performed by Willoughby city council. So now I hear stories of them chasing neighbourhood dogs around. However, I'm yet to see one at all!

Sherryl said...

Did you see the birds of paradise on "Planet Earth" on the ABC on Sunday night? I think he said they'd found 12 species in New Guinea (might be wrong about the location). Amazing feathers and plumage. Loved the male who did all that tidy housekeeping to attract the female, when she came along he did a very elaborate dance in his blue skirt thing (stunning) and she just wandered off again, uninterested! Maybe he should have offered to do the dishes as well.

Snail said...

:) I've only ever seen female Victoria's riflebirds (one of the Queensland birds of paradise) in the wild. They're very good at begging for plum jam at Paluma, N of Townsville. But I have seen a gang of male red birds of paradise at the Jurong Bird Park in Singapore. They were shaking their tail feathers all right.