"Nothing in this changing world is secure. I may not be so lucky next year." In a turbulent world, Pat Baskett is heartened by a rare appearance of an elusive migratory bird at her home.
This week a pīpīwharauroa/shining cuckoo arrived in our garden - as one, or more, always does in late September or early October. The distinctive whistling call with its final descending note is a comforting assurance some aspects of the world remain unscathed by current events and ecological changes.
For traditional Māori, the pīpīwharauroa’s arrival announced the time to plant kūmara. This was earliest in the north where the bird arrives from late August. But its habitat extends throughout the country right down to Rakiura/Stewart Island - well beyond the range of the kūmara.
Much less is known about this tiny migratory bird’s journey to and from the Solomon Islands or the Bismarck Archipelago than that of another migratory bird - the kuaka/bar-tailed godwit. Several kuaka have achieved fame by carrying radio-location devices on their bodies for their journeys to Siberia or Alaska. Their arrival back here in flocks of thousands spectacularly transforms certain shore areas, such as Miranda in the Firth of Thames.
Hearing the elusive pīpīwharauroa is one thing: seeing it is quite another. It’s the size of a sparrow but sleeker. Its call is described as “ventriloquistic” - you hear it close by but when it moves you realise it was somewhere further away. If you’re lucky you will glimpse the iridescent flash of its blue-green upper feathers and its pale breast striped with dark green.
Originally birds of the forest, they are insectivorous, timing their arrival for when the kōwhai is in flower and caterpillars of moths and butterflies are emerging. Now they are found in gardens and orchards where their diet includes scale insects that afflict crops and pear and apple trees. Their digestive system enables them to eat caterpillars that are toxic to most other birds, such as the yellow and black monarch butterfly caterpillar.
Traditional tangata whenua explanations for the disappearance of pīpīwharauroa in winter were that it hibernated in holes in puriri trees or in crevices in rocks, or that it spent the winter somewhere in Hawaiki. This latter belief was allied with knowledge of the other native cuckoo - the koekoeā/long-tailed cuckoo which over-winters in various Pacific islands and is thought to have inspired early navigators with confidence that land existed further south.
In December 2014, the Cuckoo Migration Project was started to study the migration of shining and the more rarely seen forest-dwelling long-tailed cuckoo. Three pīpīwharauroa (which weigh 25g-30g) were caught near Kaikōura and at Le Bons Bay, Banks Peninsula, and fitted with devices weighing 1g.
The aim of the study was to find out exactly where they went and whether their flight was non-stop - important knowledge for a species whose habitat is reducing at both ends of their path. My failure to find any follow-up information suggests the birds’ journey was compromised by the extra weight or the devices fell off.
The English name - shining - was given by an early English ornithologist who saw the specimen collected by Georg Forster in Queen Charlotte Sound, the naturalist on Cook’s second voyage. Did Māori convey the information that this beautiful small bird laid its egg in the nest of another, most frequently that of the riroriro/grey warbler? We don’t know but it was quickly identified as a cuckoo.
Speculating how pīpīwharauroa insert an egg into the pendulous nest of the riroriro has exercised the imagination of ornithologists, who’ve come up with three possibilities. Some suggest the female has a cloaca it can extend into the tiny opening in the side of the nest, similar to the method of one Australian cuckoo; others that the bird lays elsewhere and carries the egg in its beak to the nest.
WRB Oliver, in his classic New Zealand Birds, records this description: “The pipiwharauroa clings to the nest, forces itself through the narrow opening, breaks a way through the opposite wall, sits on the nest with its head protruding from one side and its tail from the other, lays its egg and leaves …”
The returning riroriro apparently repairs the damage and incubates the strange egg sitting on top of its own. On hatching, the pīpīwharauroa turfs the riroriro babies out.
More accessible alternative nests exist and eggs are said to have been found in those of the pīwakawaka/fantail, tauhou/silvereye and miromiro/tomtit.
The riroriro, having raised their own young before the cuckoos’ arrival, have a prodigious reputation as parents. Oliver recorded cases of both parents feeding other cuckoo fledglings besides the one they reared.
But maybe pīpīwharauroa are not totally negligent. Birdwatchers also describe seeing cuckoo parents perched nearby, watching or overseeing the care their young are receiving.
Walter Lawry Buller, in his 19th Century classic Birds of New Zealand, believed the shining cuckoo was “an inhabitant of Australia, and probably New Guinea … It makes its appearance, year after year, with surprising punctuality”.
He refers to “a pencil-sketch which I made of a captive bird as it rested quietly on the paper-basket in my study” as the source of the illustration made later in London by JG Keulemans.
Nothing in this changing world is secure. I may not be so lucky next year. Sightings of pīpīwharauroa recorded in Wellington have reduced by 35 percent in 2018-2021, according to a major study, “State and trends in the diversity, abundance and distribution of birds in Wellington City”, published in April this year. The study analyses information from five-minute bird counts carried out at 100 bird count stations in forest habitat throughout Wellington City’s parks and reserves network each year between 2011 and 2021.
The significant increase in most species is attributed to the “halo” effect of the predator-free Zealandia sanctuary which provides source populations, but also to the efficacy of local volunteer predator-trapping projects. The decrease therefore in pīpīwharauroa is an anomaly, especially as its host bird, the riroriro remains abundant.
We can only look therefore to its winter destination - the Solomon Islands where tropical forests have provided the basis of the local economy for more than 30 years. In June last year, the Guardian reported that if logging continued at its current rate, natural forests would be exhausted in 15 years.
While Solomon Islanders regret the loss of the forest and the effects of logging on fresh water in rivers, they also appreciate the communication benefits of paved roads and sometimes schools and health clinics that logging revenue provides.
