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Brush work

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Dr Ann Goeth continues an examination of Australian brush turkeys who have become very frequent residents in some areas of Sydney.
Brush turkeys are definitely in quite a few suburbs north of the Parramatta River, locations where they haven’t been seen for many years. When she began her studies of brush turkeys in the early 2000s at Macquarie University, Dr Goeth applied for a permit to collect eggs and was told she could only collect them north of the Hawkesbury River because they were so rare to the south. That is no longer the case. 
The adults don’t fly much but the chicks are able to cross rivers and cover large distances. Just recently Dr Goeth saw one at Concord and a recent article in National Geographic noted some on Military Rd in Cremorne, not far from a moist gully.

Historical records also show they have been in the Royal National Park in Sydney’s south, the Auburn Botanic Gardens and even Jindabyne. Brush turkeys are regaining their original Sydney range just as they did in Brisbane some 30-40 years ago. Then there were also a lot of complaints from local residents but Brisbanites gradually came to accept that if their gardens were in areas that the brush turkeys used they had to share their gardens with brush turkeys. All images on this page of adult Brush Turkeys are from local northern Sydney gardens (images by Paul McQueen).

Today their range extends from the Illawarra in the south all the way to Northern Queensland where they share their habitat with the orange-footed megapode. This species is smaller but its mound is much larger and the parents form monogamous pairs, a behaviour not seen in brush turkeys. Brush turkeys males are polygynous and the females polyandrous, each having multiple partners.

Second storey veranda visitor, Sydney suburb of Gordon 
The males construct the incubation mounds and the females walk around to inspect each mound. A female will dig some test tunnels and use the temperature sensor in her palate to test the temperature. This can be done over several days to see how stable the temperature is, 33°C being ideal. Given that there are many mounds to choose from such behaviour is a reflection of the cognitive abilities of brush turkeys A female will eventually choose one site. However the male demands she mate with him before she gains access to his mound. 

This means the male fertilises her eggs but the egg she lays in his mound may have been fertilised by another male. Females only produce one egg at a time, each weighing 13 to 14 percent of the female’s bodyweight. If there is enough food, that female can produce another egg four days later. This breeding cycle starts in about August, depending on the amount of rainfall, and finishes in January.
A successful male can have up to 50 eggs in his mound and can have two or three mounds at the same time. There is a lot of maintenance work for each mound. Brush turkeys can most likely sense when it’s going to rain which prompts them to rake up more material to put onto the mound, stopping it from becoming too wet and too cold. They also open the mound up on hot days. Eggs have an average incubation time of 42 days but, if the mound is colder, this can extend to 60-70 days. 

The mound only gets used for one breeding season. In the next breeding season some males might uild new ones on top of the old ones while others build new mounds from scratch. There is mound predation. In some areas it is goannas, snakes or dingoes that steal eggs. In Northern Queensland there are also wild pigs. Brush turkey males will defend their mounds quite vigorously, attacking the tails of goannas and snakes. Indigenous people have also been known to feast on these big eggs. Dr Goeth first encountered megapode birds on an island in Tonga.

She was studying the Tongan megapode that lays its egg in volcanically heated soil. Dr Goeth was intrigued as to how chicks could develop behaviours and survive without any parents. Back in Australia she incubated eggs of the brush turkey at the university, then observed them before releasing them back to their original habitat. Most observations were done in a large aviary in a rainforest on the hinterland of Queensland's Sunshine Coast.

To test the brush turkey chicks’ reactions to predators Dr Goeth trained a sheepdog and a cat to walk through the aviary on a harness. She also used a rubber snake that was pulled through the aviary and a silhouette of a bird of prey. With the bird of prey the chicks mainly ducked down, relying on their camouflage. They ran away very quickly from the dog and they also ran away from the snake but only at the last minute. They didn’t really know how to respond to the cat, basically ducking down or running away too late so the cat could have easily caught them. 

Growing up fast: One day old chick and Brush Turkey egg. (Image from Ann Goeth)    
Dr Goeth realised the chicks did not how to behave with an introduced predator like the cat, which explains why so many chicks get killed by them. People don’t see that many chicks because they like to hide in thickets near the mound. They also grow up really fast (they start growing adult-like black feathers after two weeks) and by two months look like miniature adults so they don’t stay in the cute chick stage for very long. At Taronga Zoo the chicks have become so used to humans they don’t even exhibit those hiding behaviours.
Brush turkeys are uniquely fascinating and there is attention to detail in all their brushwork. 

Dr Ann Goeth was interviewed for A Question of Balance by Ruby Vincent. Summary text by Victor Barry June 2016.

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