Our surprising kookaburras
Most Australians know kookaburras as cheerful birds that visit the barbecue for a handout of meat, but they also have a far more insidious side.
Tim Low lives in a state of perpetual surprise at everything wild and alive. His response is to write searching books, Australian Geographic articles and this blog. His book Where Song Began (Penguin, 2014) recently became the first nature book ever to win the Australian Book Industry Award for best general non-fiction. Tim’s newest book is called The New Nature.
AUSTRALIA’S KOOKABURRAS include the world’s largest kingfisher. Gigantic kingfisher and great brown kingfisher were 19th century names for these birds, before we adopted kookaburra, from the Wiradjuri people of NSW.
Although Australia is considered the home of kookaburras, it only has two species compared to three in New Guinea – or four if you count the shovel-billed kookaburra, which is also called the shovel-billed kingfisher because it is in a different genus. It digs up rainforest worms with its hefty bill.
The blue-winged kookaburra begins its day with a laugh that ends up more like a choking cough, as if it suddenly forgot the joke. It is the main kookaburra in northern Australia, and New Guinea has it also. The rufous-bellied kookaburra and spangled kookaburra, both of New Guinea, sound like yapping dogs. These three birds are closely related to the laughing kookaburra, which is found throughout eastern Australia and in southwest WA and is the species most Australians know.
Kookaburra chicks are blind and naked at birth but very aggressive, jabbing each other’s heads with special hooks on their beaks that only the chicks possess, for use as weapons against each other. In fact, many laughing kookaburras commit siblicide – killing fellow nestlings – while very young. The mother lays three eggs, but the two chicks that hatch first often peck the third to death. Or sometimes the first two grab all the food brought to the nest and the third starves to death.
A kookaburra chick is far more likely to be stabbed to death by a brother or sister than taken by a predator. This cruel situation exists because it maximises nest success. Should the first egg fail to hatch, the chick from the third will survive. Eggs often fail to hatch. Siblicide is more likely when kookaburra parents are unable to bring much food to the nest because they have only secured small territories. Under such circumstances, the third chick is often smaller than its siblings, making it easy to kill.