Nature can always surprise. Just when you think you can take something for granted, it turns out there’s an exception. Like in this case. Most people take it as a given that birds are born from eggs tended to by at least one parent. The eggs then hatch into small, defenseless chicks that are completely dependent on parental care. Yes, this is true for the vast majority of birds, but not for the Australian Brush-turkey.
This distant relative of the domestic fowl belongs to the Megapodiidae family, along with 21 other species. Translated from the Greek, it means “big foot,” which is a fitting name indeed. Looking at its photo, the huge feet seem out of place on a body of this size. It’s as if I can hear you asking why nature gave them such seemingly absurdly oversized feet. And while you’re asking, let me answer your curious question.
As you know it is part of typical bird etiquette to build nests and care for eggs, and then the nestlings. Even the Brush-turkey builds a nest – and not just any nest! The Brush-turkey nest is a structure that overshadows that of any other bird nest in the world. Literally. It is a pile of leaves, twigs, sand, debris, and other material that stands about one meter high and 3 to 4 meters in diameter. The largest ever recorded was 3 meters high, and 18 x 5 meters wide (10 x 59 x 16 feet). Such a monumental structure includes material weighing well over 50 tons!
This architectural giant is built by the male alone, using only his own feet. Thus the size of their feet. For more than a month, he toils up to 7 hours a day to pile up more than 50 kilograms / 110 pounds of material every day.
But why build such a huge nest at all? The first reason can be explained by comparing it to our own species. Simply put, a huge nest makes a much bigger impression on females than a small molehill. The second reason is more complicated to explain.
The mound serves not only as a nest, but also as an incubator, substituting for the animal heat of the parent. This is because Brush-turkeys do not warm their eggs directly, but use various external heat sources to do so. The heat in the mounds is generated by billions of microscopic organisms, mostly fungi, whose respiration keeps the developing embryos at an optimal temperature of about 33 degrees Celsius (91.4 Fahrenheit). Other species in the same family use solar or even geothermal energy to do the job.
The male’s role in life is therefore directly tied to the construction and defense of his monumental nest, as well as its ongoing maintenance. Without a proper nest, the male would not have the opportunity to mate.
The holder of a nice nest, or even nests (he can have more than one), can thus enjoy greater attention from the females. One female at a time. If it’s quiet, the female will spend up to 45 minutes laying her egg, but if there’s a queue of other interested females behind her, she’ll have to move faster and cut the time down to about 15 minutes. Sometimes there’s even a quarrel between the females. Well, there is a lot of demand for a good male.
You could say that the male does all the work, but don’t be mistaken. Brush-turkeys are one of those birds that lay extremely large and yolk-rich eggs for their size. Producing such an egg takes a lot of energy. Females have an unusually long fertile period, lasting several months. During this time, they can lay about 30 eggs, which is about three times their body weight in total – exhausting work.
Throughout the breeding season, which lasts most of the year, the male must tend to the nest. Sensitive thermoreceptors on his beak allow him to control the temperature and regulate it by adding and removing material. Too low or too high a temperature would mean death. It’s also important to get air to the eggs so the embryos don’t suffocate. And of course the mound has to be watched, because Monitors, Foxes and (in large numbers) humans also like to feast on eggs full of nutrients.
Eggs with a large amount of yolk are beneficial for developing chicks. It allows them to stay in the egg up to 71% longer than birds with similarly sized eggs, but less yolk. As a result, they are fully developed when they emerge from the shell after 50 to 96 days. With a mighty kick of their big foot, they break the thin shell of the egg, dig themselves out of the mound, and are able to fly almost immediately. They will probably never meet their siblings or parents. From the first moment, they are able to fend for themselves. The hatchlings of all Megapodids thus come into the world as the most developed of the entire bird kingdom, and it is largely thanks to their unique homes before hatching.
The male Australian Brush-turkey I photographed near Cairns, Australia, clearly demonstrated how effectively he can defend his mound from potential predators. He turns his back to the intruder and uses his powerful legs to throw branches, stones, leaves, in short, anything that gets under his feet. This behavior is truly unique and is one of the few recorded cases of animals using weapons.
As a result of this fierce defense, I slowly began to turn into a compost mound as I studied and photographed the bird. It wouldn’t be long before the female Brush-turkey laid her first eggs right in my lap! At this point, I was very glad that I had a protective filter and lens hood attached. Both proved effective in preventing damage to the sensitive lens, even though they were not designed for this level of mess.
The Australian Brush-turkey is a fascinating creature, and it was my privilege as a biologist to be able to spend time learning about these birds, studying them, and photographing them. I hope that by bringing you the story of the Australian Brush-turkey, I have inspired you to appreciate the wide range of unique birds in our world and some of the process that goes into studying them!