Cuckoo for Cuckoos

Springtime in the bird world means a flurry of breeding activity. Many birds are looking their best and advertising their attractiveness to potential mates with calls and displays. However whilst most birds follow the standard ‘find a mate, build a nest, lay eggs, raise young’ (with some slight variations), cuckoos do things a little differently. They are often seen as the ‘absent parents’ of the bird world – they lay their eggs in other bird’s nests and then they take off, leaving exhausted hosts trying to raise a chick that often grows bigger than them. The chicks too, need to work hard to survive. Many, upon hatching, instinctively push any other eggs and nestlings out of the nest, keeping the host parents just for themselves. Others grow incredibly quickly and demand all the food the host parents bring, so they simply outcompete any host chicks. It’s Survivor: Bird World.

 

Whilst brood parasitism can be cruel, it is incredibly fascinating. Cuckoos and their hosts are locked in an evolutionary arms race trying to do their best to outwit each other. The only way for the cuckoos to survive is to trick their hosts, and the hosts cannot afford to always be raising cuckoo chicks, so they need to evolve to recognise and reject cuckoo eggs (which look incredibly similar to their own). Superb Fairy-wrens have been shown to be incredibly good at this. They emplo a very unique tool. Expectant Fairy-wren mothers teach their unhatched offspring a secret password that they'll later need to get fed (they also teach this to the other parent and helpers). The cuckoo chicks, who don't know the password, are out of luck and if the nest is overrun with chicks that don’t know the password (which is, by the way, unique to each Fairy-wren mother), the Fairy-wrens will simply abandon the nest and try again.

 

Cuckoos are incredible tricksters though, and most manage to fool host birds. They also have to get their timing just right – having an egg ready to lay at the same time as a host, and be able to sneak in to lay it without being detected. It’s a very delicate balancing act that often requires both the male and the female cuckoo to work together.

 

Australia has 12 species of cuckoos and the Pheasant Coucal is the only one what builds its own nest. We also have both the smallest cuckoo in the world: the Little Bronze Cuckoo, weighing 17g and the largest – the notorious Channel-billed Cuckoo weighing a hefty 630g and resembling a flying dinosaur with that incredible beak. It is also one of the two species that drive people a little crazy on the east coast. Both the Channel-billed Cuckoo and the Eastern Koel migrate from northern Australia and even Indonesia and Papua New Guinea, heading south in order to breed from August and calling all day AND all night. The calls can be annoying. loud and sometimes interfere with our sleep, but hats off to them, they are doing so well because their host birds are doing well – both species target our larger urban birds; from Magpie-larks and Wattlebirds to Australian Magpies and Australian Ravens. Aside from these big and well-known cuckoos we have a range of smaller, beautifully patterned species including the Shining Bronze-Cuckoo, the Horsfield’s Bronze-cuckoo, and the Fan-tailed Cuckoo amongst others.

 

So next time you hear the loud call of one of our cuckoos or perhaps see a giant chick demanding dinner from a tired looking host bird, have a think about the cunning cuckoos and the amazing efforts they go to in order for their species to survive. Its far from ‘absent’ parenting…

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