Shining cuckoos, shonky parents

Last updated 12:33 09/11/2012

Shining cuckoos or pipiwharauroa take a "hands-off" approach to parenting, preferring to let another bird do the grunt work of raising their babies; while they soak up the sun, gorge on insects and then fly off to the Pacific for winter.

grey warbler feeding shining cuckoo1 (photo: Malcolm Pullman)

The tiny grey warbler parents take on the task of feeding the enormous shining cuckoo chick. Photo: Malcolm Pullman.

In New Zealand the shining cuckoo is our harbinger of spring. That distinctive pweeep-pweeep-pweeep-pweeeep-pweeeeep-pweeeep-pwwwaaaaooooo sound (listen here if you don't believe me!) has been described as sounding like a sheep farmer whistling his dog.  We start to hear that sound over here around the end of September, and it's a lovely reminder that warmer weather is on the way.

The journey that the shining cuckoos take from the western edge of the Pacific, past Australia and on to New Zealand is thousands of kilometres. That's quite an impressive journey for a bird not much bigger than a blackbird!

The incredible journey of cuckoos leaving the Pacific was recognised by Polynesians who watched the annual migration and guessed there must be land south of the Pacific Islands, perhaps giving them the motivation to jump into their waka and seek out New Zealand.

Most cuckoos around the world are "brood parasites". This means that they don't raise their own chicks, instead laying their eggs in the nests of other birds who do the chick-rearing for them.

To some mums and dads out there, the shining cuckoos' approach to parenting might sound like they have it made. After arriving in New Zealand, they set about finding a suitable foster-parent, which for the shining cuckoo is invariably the tiny grey warbler.  How the pipiwharauroa managed to get her (comparatively big) bottom into the tiny pear-shaped grey warbler's nest is quite a puzzle. It turns out the cuckoo perches on the rim of the nest, pokes her bottom into the hole and carefully lays her egg amongst the grey warbler eggs.

This is where the fun starts.  Evolution has given the shining cuckoo egg an advantage, since it hatches before the grey warbler eggs, and once hatched the tiny chick actually pushes the remaining eggs or even chicks out of the nest.

From that point on, the shining cuckoo chick takes up all of the grey warbler parents' attention and energy, and being much larger, requires a constant delivery of spiders and insects. Grey warblers are tiny (weighing as much as two ten-cent pieces), and can look quite comical feeding their gargantuan cuckoo chick. They are dedicated parents though, and will feed the impostor chick for four weeks (they have even been seen hanging around their fledged chick to make sure it's OK) before it flies off to join its fellow cuckoos in the Pacific.

It's not all bad news for the supernanny grey warblers though, since they somehow manage to raise a clutch of eggs before the shining cuckoos arrive, giving them a chance to raise their own offspring first.

The story of the shining cuckoo and grey warbler has always fascinated me. I've never seen a shining cuckoo chick in a grey warbler nest, but a shining cuckoo arrived in our silk tree on Boxing Day last year and was beautiful to see.

Have you ever seen a shining cuckoo? Or just heard them? Did you know about their pretty selfish breeding tactics?

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