Cheeky cuckoo chews caterpillars
It was with some surprise and delight that we noticed a shining cuckoo in our garden one morning recently.
It was the first one we had ever seen and we admired the stripey tummy and shiny green wings on this fast little bird.
But then we saw something that really surprised us. It settled on our large and newly stripped swan plant, filled with hungry caterpillars and lots of the bulbous seed sacks (named swans for their shape) and began swallowing fat caterpillars, which we thought were safe from birds because they are poisonous.
The swan plant, ( Asclepias physiocrat) is a member of the milkweed family and is toxic in all its forms. None of it should be ingested and care in educating children is prudent.
The monarch caterpillars take on this poison and use it as selfdefence, advertising the fact with their bright colours to predators. The butterflies carry this on, with the females more toxic than males, with both having reducing toxicity with age.
Any bird eating a monarch caterpillar or butterfly becomes sick and learns not to do it again. But not the cuckoo. It feeds on them to fatten up for the return flight to the islands for winter.
Described as parasitic, the shin- ing cuckoo or pipiwharauroa ( Chrysococcyx lucidus lucidus) flies to New Zealand in spring, where it spends the warm months of the year before flying back to its Solomon and other Pacific Island forest habitat.
While here, it breeds and lays its eggs in another bird’s nest; in the North Island this is usually the grey warbler’s or riroriro’s ( Gerygone igata) nest. Thankfully, the tiny warbler gets to raise one batch of young in August before its next nest is infiltrated by the cuckoo, which arrive in September.
If the cuckoo mother hasn’t done so already at the time of laying, the cuckoo chick sets about turning the grey warbler eggs or chicks out of the nest as soon as it has the strength to do so.
Now, it becomes the sole recipient of its foster parents’ care. How the larger cuckoo lays its egg in the small entrance to the warbler’s nest is so far a mystery, but it is possible it carries it in its beak and pops it into the tiny hole.
If you live in an area with grey warblers, you are likely to have the little shining cuckoo nearby too.
Their call is a series of upward whistles, followed by downward notes and it can be confused with a thrush’s song. With a striped belly and and green and brown colouring, the cuckoo is well camouflaged and can be close nearby, but practically invisible.
As well as being the only animal tough enough to eat monarch butterfly caterpillars, it is also one of a small number of birds that can feed on the hairy caterpillar, a recent import into New Zealand. The hairy caterpillar or gum leaf skeletoniser ( Uraba lugens) is now found in several areas of the country and is considered a pest species both here and in its native Australia.
Its hairy spines contain a venom which is released from the merest brushing of skin against this creature and can cause irritation or painful welts. Even the dead skin shed from a caterpillar can sting.
So while the cuckoo keeps the warbler and monarch butterfly population in check, it does the same with the hairy caterpillar, to our advantage.