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.

Juicy: One of the lucky ones – a monarch cater­pil­lar that es­caped be­ing eaten by a shin­ing cuckoo.

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