Nature’s Corner – Early to Late Autumn 2007

Not Dying, just Deciduous!

A kotukutuku tree in autumn

Kotukutuku / Tree fuchsia (Fuchsia excorticata). Amidst the many shades of green in the Karori Sanctuary bush, one native tree species breaks the evergreen tradition and acknowledges autumn with a modest show of alternative foliage colours followed by leaf fall. This photograph was taken at the top of the Swamp Track on 28 May 2006, and is one of the better examples of kotukutuku autumn colours I have encountered in the Sanctuary. When I last checked this tree, on 12 May 2007, it was still very green with only a scattering of yellow leaves, although many others in the Sanctuary had already dropped much of their foliage. I presume that a particularly sheltered location allows it to hold on to its leaves for longer. I was intending to return on 28 May to make a comparison with last year’s display, but unfortunately this has not been possible.

Unlike the deciduous trees of the northern hemisphere, leafless kotukutuku are far from dormant. They produce flower buds and come into bloom during their leafless period. The nectar produced by their flowers is a very important winter food source for tui, korimako / bellbirds and hihi. The Karori Sanctuary has the largest stand of kotukutuku south of the Tararua Range and the protection of our pest-proof fence stops possums from gobbling the flower buds and depriving the birds of their essential nectar supply. This is a key species in the Sanctuary’s ecology and fundamental to the re-establishment of thriving populations of korimako and hihi. We should always treat these trees with respect. They are essential to the healthy natural ecosystem we want to restore.

Autumn Butterflies

Kahukowhai on koromiko © Allison Buchan

Kahukowhai / Yellow admiral (Bassaris itea) & Kahukura / Red admiral (Bassaris gonerilla gonerilla). At the beginning of March, I was quite concerned at the lack of butterflies. The koromiko (Hebe stricta) was flowering but I saw only bees collecting the nectar. There has been talk recently of a worrying decline in the native butterfly population. Introduced predatory and parasitic wasps are suspects in the case. Both attack caterpillars. The predatory wasps eat them and the parasitic wasps lay eggs in them, leaving their offspring to devour the caterpillars from the inside. I had not noticed many wasps about, but I was ready to blame them nevertheless.

Kahukura on koromiko © Allison Buchan

Happily, when I walked a section of the inner boundary track a couple of weeks later, I found the butterfly drought had broken. Any koromiko bush I encountered had one or two kahukowhai sipping nectar from the flowers. The absence of kahukura was puzzling though. Usually they arrive first. As caterpillars they live on ongaonga / tree nettle (Urtica ferox), a plant that is hazardous to humans. Could ongaonga have been sprayed in the vicinity, I wondered, resulting in a generation being wiped out? I was relieved to find on my next visit that kahukura had joined kahukowhai in the koromiko feast. Why they were late remains a mystery. My impression was that I saw fewer kahukura than in other years, but one cannot draw firm conclusions from intermittent visits.

A tattered kahukura sunbathing © Allison Buchan

In late April when I photographed this tattered specimen basking on the wide metal band that tops the Research Area fence, I wondered if it would be the last one I would see in the Sanctuary until next spring. But May has been unusually dry and mild and the odd butterfly is still encountered on bright sunny days when there is little wind. I have seen them in flight or basking with wings spread wide to soak up as much warmth as possible, but I don’t know what they are feeding on now. The koromiko had only an occasional flower spike remaining at the end of April and has since gone to seed. My most recent sighting was a kahukura sunbathing on the north face of the Upper Dam. Those that emerged from their chrysalises late in the autumn will hibernate through the winter and re-emerge in the spring.

Some Autumn Flowers

Akakura flower cluster

Akakura / Scarlet rata vine (Metrosideros fulgens). When writing about the summer flowering of our northern rata (Metrosideros robusta) and the pohutukawa (Metrosideros excelsa) in our previous edition, I speculated that akakura (Metrosideros fulgens) might follow their example and put on a notable floral display, but this had not occurred by the end of autumn. As usual the vines growing up on top of the western scarp, just south of the Weka Fence gate adjacent to the boundary fence, have been flowering since the end of February, but the flowering has been sparse and intermittent. They can only be seen from the inner boundary track. On the western scarp, as seen from the Lake Road mesh safety fence, I noticed on 12 May five flower clusters above and slightly to the right of the cascading kiekie (Freycinetia banksii). On the same day a small patch of scarlet was visible on the scarp when viewed from the Tui Terrace-Union Mine junction. Flowers were also reported in late May to be visible below the Bentley picnic table site on the Round the Lake Track. Overall, a lukewarm performance from akakura this autumn, but it could still redeem itself in winter.

Maire tawake flowers Photo by Tom Lynch

Maire tawake / Swamp maire (Syzygium maire). The grove of trees that meets the western side of Lake Road just north of V transect has been flowering since late March. The flowers are white when they first open but discolour as they age. They have a rather similar design to Metrosideros flowers and as it happens Metrosideros and Syzygium are related in that both belong to the myrtle family. Flowers are in clusters, the most prominent feature is a brush of stamens and these stamens fringe small cups of nectar with central styles, each tipped with a small stigma to receive pollen. Birds that visit to eat nectar inadvertently pick up and transport pollen and pollinate the flowers. The stigma is receptive before a flower’s own stamens have shed their pollen, so if things go according to plan the flower will be fertilized by pollen brought from elsewhere.

Male kanono flowers

Kanono (Coprosma grandifolia). Kanono is dioecious. Some kanono have male pollen-producing flowers like this. Others have female flowers that must be fertilized by pollen before fruit can grow. To get pollen from a male to a female, kanono has opted for the economy plan. It doesn’t bribe anyone with nectar, it sheds its pollen into the air and relies on air currents to waft or blow it about. Some will come into contact with flowers of the opposite sex and the job is done. Kanono is common in the Sanctuary and has been flowering since April. To find a picture of female flowers, refer to the Late Autumn 2005 flora edition in our Archive.

Keeping Track of Demon Grasshoppers

Don’t worry. Karori Sanctuary is not fighting off an invasion of alien insects. ‘Demon grasshoppers’ is the English translation of Deinacrida, the scientific name applied to New Zealand’s wetapunga / giant weta. The name was given in 1842 when the first scientific description of a giant weta was published. The scientist recognised that the insect under examination was a relative of the grasshopper but he obviously thought the size and appearance was scary enough to arouse the sort of horror one might feel when confronted by a demon. Maybe he received quite a shock when he first opened the package to see the new specimen.

Sanctuary conservation officer Rob Cross using telemetry gear

Twenty of our recently released Cook Strait giant weta (Deinacrida rugosa) carried tiny radio transmitters and our conservation officers were daily engaged in monitoring their movements in late March when these photographs were taken. The telemetry gear that is being held aloft emits a stream of bleeps when it picks up a signal from one of the transmitters. By moving in the direction of a strengthening signal until it becomes pervasive, the quarry is eventually located, occasionally up a tree but more usually on the ground, sheltering under grasses or among tree roots, leaf litter and other debris. Details of the location are recorded in a data folder and using a GPS device. In this way an individual’s wanderings can be mapped and measured (although we cannot know how much they zigzagged when walking from one location point to the next).

Found: a female wetapunga

A few of these heavyweights have been surprisingly mobile. This female had been released at Tui Terrace on 11 February and on 31 March was found only a few metres from the Campbell Street emergency exit. I heard that one male had been up to the eastern boundary and then crossed the valley to the western boundary. He may also have set a land speed record for his species, having reputedly travelled some 300 metres in the course of a single night, but the data collected has yet to be fully analysed and reported and more definitive information will emerge when the research has been completed.

Wetapunga 525 (deceased)

On this occasion the female wetapunga / giant weta located at the base of a tuft of grass was deceased. The recovered body rests on the blue cover of the data folder beside a stray stem of dead grass. The radio transmitter with its projecting aerial is glued to the part of the exoskeleton known as the pronotal shield or pronotum. Beside the transmitter you can see a plaque with the unique number that identifies this individual for research purposes. Attaching these things didn’t hurt the wetapunga. It is like having something glued on the outside of a suit of armour. All those released in Karori Sanctuary were adults whose natural deaths are expected as winter approaches. Adult wetapunga live only a few months, during which time they mate and females lay between 100 and 300 eggs. Hopefully plenty of this female’s descendants will be hatching out in the Karori Sanctuary next spring to carry on her genetic line.

Waiting for Lift-off

Ripe akeake seed capsules

Akeake (Dodonaea viscosa). The clusters of papery-winged seedcases that have decorated female trees turned from pale green to brown during February and March and were being gradually stripped away by wind in late April and May. Seedcases may have two wings or three. The seeds (one or several) are in the ‘blister’ at the centre. The wings provide more lift and help them float at least short distances away from the mother tree. If the seeds dropped directly below the tree, they would not be able to survive the shade and the competition for water from the tree roots. In windy weather they can travel further, either swept along the ground or sailing through the air for a while.

Takupurenga seeds fluffed for flight

Takupurenga / Coastal tree daisy (Olearia solandri). Wind power is the seed dispersal agent for all members of the Olearia genus. This particular specimen grows right beside Lake Road, against the rocky face of Bedrock Bluff, just past the Ops Shed. It was self-sown, but another one growing across the road near the Safety sign was planted. The seeds are furnished with tufts of downy hairs that fluff out on fine days, ready for take-off if a breeze snatches at them. These seeds can be dispersed over much greater distances than akeake seeds. Their downy parachutes are more efficient at keeping them airborne than the akeake’s wings.

Shape-Shifting Weevils

Four-spined weevil among akiraho flowers © Allison Buchan

Akiraho (Olearia paniculata) has minute, white, perfumed flowers (called florets by botanists) in late March and April. When I stopped to photograph some flower clusters on the bushes on the north side of the Lake Road pedestrian gate in the Weka Fence, I became aware of some tiny black insects traversing them. Peering closer, I thought I was looking at several different insect species. Or perhaps they weren’t all insects. There was one that I thought at first glance was a beetle but another one seemed to have too many legs.

Four-spined weevil looking spider-like © Allison Buchan

Spiders perhaps? There was one with peaks on its back. I knew of an Australian two-spined spider naturalised in the North Island. Wait, that leg was disproportionate, much thicker than all the others. It must be two legs held close together surely? But it wasn’t. When I got out my magnifying glass the supposed two legs were revealed to be one long snout. I was looking at four-spined weevils (Scolopterus species), and they present a very different appearance when seen from different angles. These pictures have been enlarged so you can see what the magnifying glass showed. In real life the florets are only 2 millimetres in diameter and the weevils about 5 millimetres long.

Four-spined weevil: 'Is this my best side?' © Allison Buchan

Four-spined weevils eat pollen but may also carry out some unintentional pollination of the flowers they are robbing. The akiraho flowers apparently functioned as a regular restaurant for them. As long as there were flowers on the bushes, I could find some weevils among them. And when I checked some pictures of akiraho flowers taken the previous year, zooming in for a detailed examination, I discovered four-spined weevils had been present then too, only I hadn’t noticed them.

First Fruits

Ripe kapuka fruit

Kapuka / Papauma / Broadleaf (Griselinea littoralis). On 29 June 2002 several of these trees were planted on the north side of the Weka Fence between Lake Road and Te Mahanga Track. They are now about 2 metres tall. Three of them flowered for the first time in spring 2006 – one female and two males. The female, growing directly behind the Pryde Jowsey Saunders Family seat, has since produced its first fruits. They started to colour in late April and most had ripened to dark purple by mid May.

Ripe tainoka seedpods

Tainoka / Makaka / New Zealand broom (Carmichaelia australis). There are a number of these native brooms among plantings northeast of the Lake Road vehicle gate in the Weka Fence, on the west side of the track that descends to the Keith Taylor wetland and lawn, and on a bank above Lake Road just north of Alison Morton’s memorial. Most of these produced their first flowers as December began and some successfully ripened their first seedpods in March and early April. Tainoka is a lighter green than the common introduced broom. Its seedpods are small, usually under a centimetre in length, and do not open explosively.

Hihi Herald

The second hihi / stitchbird (Notiomystis cincta) breeding season in the Karori Sanctuary resulted in a total of 69 fledglings. Not as many as the bumper first season which produced 89 but still a good result considering the cold wet spring and the late arrival of settled summer weather. That first season had the added stimulation of release into a new environment with no existing hihi population – a great incentive for rapid colonisation and not something that can be repeated. Also, one of the supplementary foods supplied in the first season was not offered in the latest season.

Adult male hihi feeding male fledgling Photo by Tom Lynch

The last hihi to fledge this season left the nest on 13 March. Parents continue to feed them while they learn by observation and by trial and error how to find their own food. The fledglings are innately curious and peck and poke at things, which is a good start. This adult male (Orange-Red Metal) is introducing the fast food option to his son (White Metal-Green Orange), one of a clutch of three. They are perched beside a supplementary feeding station containing a sugar water dispenser. Dad has been in, sipped some sugar water, and is pouring it down junior’s throat. In a few days, impatient junior will be following Dad or Mum inside the feeding station and will be inspired to explore those holes at the base of the feeder. Eureka! Sticky beak has found the horn of plenty! The tricky part is often finding one’s way out again. The station is inside a cage with small entrance holes to screen out monopolistic tui. Fledglings can get very distressed if they have forgotten how they came in and think they are trapped. One side of the cage can be left open temporarily until they have gained confidence and figured out where the holes are.

Juvenile, but soon to be adult, male hihi disturbed while eating poroporo fruit Photo by Tom Lynch

Fortunately, hihi prefer the nutrition and variety of wild foods and the fast food does not become a mainstay. During autumn, as the youngsters learn how to find fruit, nectar and invertebrates to eat, the use of feeding stations declines. Once independent of their parents, they often travel about in small groups. It’s a time of wide-ranging exploration. Within about three months of fledging they have moulted into their adult plumage. The beginnings of adult plumage are just starting to show on the young male in the picture. He has been enjoying a meal of poroporo (Solanum laciniatum) fruit. They don’t wait for it to ripen fully but start eating when it is yellow. They hang upside down, suspended from a stem, to reach the dangling fruit. Some have a precise technique, eating out the bottom of fruits and reducing them to hollowed-out bell-shapes. Others are messier, but maybe they just need practice. Karamu, mahoe, mapau, ngaio and pate fruit are also on the autumn fruit salad menu. But hihi like their meat too. A lot of time is spent gleaning invertebrates from tree trunks, branch joints, supplejack tangles, foliage and leaf litter. Let’s not forget the sweets: maire tawake flowers have been a popular source of nectar and akakura flowers are also being visited. Kohekohe and kotukutuku will refresh nectar supplies in winter.

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Fruit to Go

Kohia fruit ripening

Kohia / New Zealand passion vine (Passiflora tetrandra). Towards the end of April globular fruits started turning orange on the female vines across the overflow channel from the restricted road access to the Visitor Centre. Look for them when you are near the bollards. Since this photograph was taken they have turned a deeper orange. Some of the ripe fruit was picked in May and the seeds harvested for future restoration plantings inside the Sanctuary. Cuttings have also been taken.

Ripe mahoe fruit

Mahoe / Whiteywood (Melicytus ramiflorus). Mahoe flowers featured in our previous edition. This is the fruit that develops after the pollination of female flowers. It ripened through late summer and early autumn. Individual fruits are 4 or 5 millimetres across. Many trees had heavy crops including the one at the southwest corner of Round Lawn where this photograph was taken at the end of March. There was still plenty of fruit on it in late May, perhaps because the tree is low to the ground and birds are deterred by the human activity on the lawn.

Fallen ripe totara fruit

Totara (Podocarpus totara). When you are walking the Totara Track (also known as the extension to Te Mahanga Track) look on the ground beneath two of the three large totara trees that are a feature there, namely the northernmost one and the central one beside the totara information panel. These are female trees and you should see some small fruits like these. The first few to be noticed were brought down by a heavy downpour on the morning of 2 May. The red part, called the aril, is a food treat for birds, to cause them to swallow the attached green seed and deposit it elsewhere in their manure. Look up at the crown of the tree and see if you can spot any birds that might be eating fruit. A group of young male hihi have been paying regular visits. They seem to be primarily hunting insects but probably take some fruit as well.

Secret Seeding

Hangehange seeds exposed

Hangehange (Geniostoma ligustrifolium var. ligustrifolium). If you peer into a hangehange bush in March or April you will probably see small pointed green capsules (often mistaken for unripe fleshy fruits) and the dry, blackened remains of empty capsules. Catching them in the act of releasing their seeds takes a lot more searching, which is strange because they do not employ the explosive method of seed dispersal. Sometimes I think they are being deliberately secretive to protect their privacy from camera snoops like me. Hangehange seeds are embedded in an orange or yellowish-orange placenta that is left exposed when the capsule splits in two and gapes open. I did observe a hihi deftly harvesting three of these little coloured food-parcels from open capsules one day in late March. So perhaps small birds are responsible for their prompt disappearance.

Fruit or Flowers?

Whauwhaupaku female flowers and flower buds

Whauwhaupaku / Houhou / Five-finger (Pseudopanax arboreus). ‘Fruit, of course,’ is the usual answer when shown a picture like this, but surprisingly that answer is wrong. These are the female flowers and flower buds. What appear to be fruit are flower ovaries. They can become fruit, but only after the flower has been fertilized with pollen. The minute, white, splayed stigmas atop the ovaries at the bottom centre of the picture are the giveaway. They are poised to collect pollen brought by insects from male-flowered trees, because whauwhaupaku are usually dioecious (having male and female flowers on separate plants). The flower buds are the ones with domed tops. The dome is made up of 5 minute petals, and when they open the flower does look briefly like a proper flower, though a very insignificant one, being only 3-5 millimetres in diameter. However, the petals, having fulfilled their protective function, soon fall off, leaving only the essential stigma. At the end of autumn some whauwhaupaku on sunny ridges will be starting to flower, but down in the valley flowering usually commences in late June.

To see a picture of the male flowers, refer to the Early Winter 2005 flora edition in our Archive.

Pontoon has Perching Potential

Pontoon section being towed on Roto Kawau

This was the scene on 21 April as sections of a galvanised steel pontoon that had been lowered by crane into the water at the northern end of Roto Kawau were towed up the lake to the assembly site near the southern shore. Two ‘gondoliers’ equipped with paddles rode on deck and helped to manoeuvre each section into position when the destination was reached. Since then divers have secured the floating sections to anchor blocks. Fitted and bolted together, rather like a large-scale ‘meccano’ project, the pieces form a pontoon walkway that crosses the Morning Star inlet between Kawau Point and the south end lawn. It will extend the Keith Taylor Wetland Trail, providing visitors with an on-water experience. Work is continuing on the Kawau Point access track to the pontoon.

Welcome swallow on boat ramp railing

With all the human activity generated by its construction, birds have been keeping well away from this strange new contraption, but once it has become a settled part of the landscape I anticipate they will find ways of making use of it when human pedestrians are scarce. Welcome swallows already find the boat ramp railings at either end of the lake convenient parking places and the pontoon railings should be equally attractive to them. Ducks, both native and introduced, are sure to appreciate such an extensive haul-out terrace with easy access to the water on both sides: just the place for them to rest between food foraging expeditions and water sports. Suitable also for kawaupaka / little shags to roost for fish-spotting or feather-drying purposes. And at night, might this be a short-cut route for a little spotted kiwi in a hurry?

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This edition of Nature's Corner was written by Karori Sanctuary volunteer Allison Buchan on 27-29 & 31 May 2007. Information about tracking giant weta and about the hihi breeding season was supplied by Sanctuary conservation officers Rob Cross and Matu Booth respectively. Thanks also to the volunteer hihi monitor who shared her observations of hihi activity in autumn and to Sanctuary operations manager Keith Calder for answering questions about the pontoon. Unless otherwise indicated, photographs are taken by Allison Buchan and are © Karori Wildlife Sanctuary. Clicking on photos will take you to a larger version.

Published 11 June 2007.