Nature’s Corner — Early to Mid Autumn 2008
Hihi Herald
Hihi fledgling Photo by Tom Lynch.
Hihi / Stitchbirds (Notiomystis cincta) in the Karori Sanctuary extended their breeding season well into March this year, presumably encouraged by the warm, dry, settled weather that dominated late summer and continued in early autumn. (In 2007, by contrast, no eggs were laid after January.) The last chick to fledge left a third-clutch nest on 19 March 2008. Two older siblings had already fledged from the same nest and this one made a grand total of 52 fledglings for the entire season. For conservation officer Ron Goudswaard this was a pleasing conclusion after a poor start. In the early stages, 'there were several abandoned nests and two females disappeared completely', he explains, 'but five females continued on to have second and third clutches. The third clutches in particular were amazingly successful so that the end result (productivity per pair) was about the same as usual.'
Maire tawake flowers in close-up Photo by Tom Lynch.
In the second week of March, one very dedicated female was discovered incubating a fourth clutch of three eggs. She 'sat very diligently until the eggs were well overdue', Ron says, so their failure to hatch was not due to any maternal neglect on her part. It is common for late clutches to be infertile. The males tend to lose their potency earlier than their partners lose interest in laying. As hihi males have a reputation for 'putting it about' with casual liaisons and bigamous partnerships, it's hardly surprising that they run out of steam.
New fledglings become independent of their parents in two to three weeks. Ron reports that in early April many juveniles were congregating in the vicinity of the maire tawake / swamp maire (Syzygium maire) grove that meets the western side of Lake Road just north of V transect. The white pohutukawa-like flowers are a ready source of nectar. Juvenile plumage is similar to that of an adult female but the 'cohort combination' of a blue band above a metal band on one leg distinguishes the youngsters
Adult male hihi dressed to impress Photo by Tom Lynch.
Adult hihi were starting to moult into a new suit of feathers as April began. The first parts of new feathers to develop are the basal quills (or shafts) and these briefly show up white as they emerge from among the old worn feathers that they will replace. They are most likely to be noticed when speckling the black hoods of the males, but soon both sexes are re-clad in sleeker, brighter versions of their previous uniforms.
Juveniles moult into their adult plumage within two or three months of the time they left the nest, so any that fledged early in the season, say December 2007 and January 2008, will have made or be making that transition by April. Adulthood brings no change in general appearance for the females, but 'the boys' are transformed with yellow shoulder flashes and breast ribbands, velvety black hoods and jaunty white ear tufts, into the natty ladies' men typical of hihi society.
White Autumn Flowers
Maire tawake fruit and flowers Photo by Tom Lynch.
Maire tawake / Swamp maire (Syzygium maire). Ripe fruits from last year's flowers were still present when this year's flowers were opening in mid to late April. It is not unusual for them to overlap. The location of the picture is just north of V transect at the western side of Lake Road. The fruit is eaten by kereru and the flower nectar by tui, korimako / bellbirds and hihi. The nectar seems to be particularly popular with the hihi who have made the most of their window of opportunity while many tui have been distracted by the abundant ripe fruit available from the exotic Himalayan strawberry trees (Cornus capitata) that grow below the Upper Dam. Flowering of maire tawake will probably continue in May.
Houhere flower and flower buds with developing seed clusters.
Houhere / Lacebark (Hoheria populnea varieties). There are some scattered, often solitary, trees in the Sanctuary and a small grove on the Valley View Track. Most flowering takes place in late March and through April. This picture was taken late in April on the Keith Taylor Wetland Trail where a houhere grows on the eastern side of the track about midway between the brushwood hide and the Weka Fence. It had been flowering since 18 March but still had some unopened flower buds. What look like green flowers are seeds starting to form from the remnants of fertilized flowers that have discarded redundant pollination paraphernalia like petals and stamens. The five-pointed central structures are each composed of five winged seeds.
A weevil among akiraho flowers © Allison Buchan.
Akiraho (Olearia paniculata). These minute but sweetly scented flowers (or florets) are frequented by some of our smaller native weevils, although whether the scent message is intended for them I don't know. The four-spined weevils that featured in our Autumn 2007 edition were there again and two other kinds that I hadn't seen before, one of which is included in this picture. It was about 6 millimetres in length. Something had obviously been eating a neighbouring leaf but there were no eyewitnesses so the weevil cannot be implicated. It might be a pollen-eater like the four-spined weevils. There are several akiraho on the north side of the Weka Fence near the Lake Road pedestrian gate and the photograph was taken there towards the end of March.
Female kanono flowers.
Kanono (Coprosma grandifolia). This species is dioecious, which is a quick way of saying that male flowers and female flowers are on separate trees. The male flowers produce pollen to fertilize female flowers that can then bear fruit. Because the male and female flowers have different functions they look quite dissimilar. They rely on wind currents, not insects or birds, to transport the pollen between the sexes, so they don't flaunt attention-grabbing petals. Instead petals are reduced and fused together in tiny pale green corolla tubes.
The picture shows a cluster of female flowers. Those lobes around the top of each corolla tube represent the tips of the fused petals. The tubes are about 5-6 millimetres long but from each one two stigmas extend for perhaps another 9 millimetres. They are poised to capture airborne pollen released by male trees. They feel slightly sticky to the touch and if you look at them under a microscope you will see a surface covered with a forest of minute glistening hairs, usually with many minute specks adhering to them.
Male kanono buds and flowers.
At Round Lawn you will see a flowering female kanono behind the Reynolds seat and for comparison a flowering male kanono (with typical dangling stamens) to the right of the tarata behind the Busby Family seat. There are many other examples to be found along Lake Road but I saw a good display of female flowers to the left of the first set of Weta Hotels.
March of the Borer Beetles
Lemon Tree Borer (Oemona hirta). You would think that a beetle commonly known as a lemon tree borer must be an exotic pest that has been accidentally introduced from overseas. Not at all, it is just a very adaptable New Zealander. The beetles are pollen-eaters but the females lay their eggs on green twigs, under bark, or in cracks, breaks, or wounds on live trees. The grubs that hatch out eat their way through the living wood, creating tunnels as they go. As long as they lived in the bush and ate the wood of native trees like rangiora, mahoe and tarata / lemonwood, humans ignored them. They didn't acquire a common name until they started making a nuisance of themselves by boring into the exotic citrus trees planted in people's orchards and gardens. Becoming a horticultural pest is a sure way of getting known and named.
Lemon tree borer out of its depth © Allison Buchan.
Karori Sanctuary has no citrus trees, but we do have lemon tree borers and plenty of traditional bush tucker for their grubs to dine on. The grubs eventually pupate and re-emerge as adult beetles in late summer or autumn to mate and lay the eggs that will produce a new generation. They have sharp little hooks on their feet to help them cling on to tree bark and other surfaces. I found this adult drowned in the historic rain gauge on Raingauge Spur on 4 March. When I fished it out I thought at first that I had rescued a live beetle because I felt it clinging to my hand, but it was just those efficient little hooks, the beetle was deceased. Notice the long antennae and the body shape somewhat like the tunga rere / huhu beetle. The lemon tree borer is another species of longhorn beetle.
This particular lemon tree borer, which measured 32 millimetres from the front of its head to the tip of the wing covers, seemed larger than others I had seen, but on 23 March an even larger one, 35 millimetres in length, turned up on the Research Area fence. It was so perfectly still as I peered closely at it and photographed it, that I assumed it was dead like the previous one and thought I would collect it and take it to the Visitor Centre. However, it had either been sleeping soundly or was playing dead as a protective device because it suddenly came to life when I attempted to remove it and was quite adamant that it did not want to accompany me anywhere. I apologised at once for disturbing it so rudely and left it in peace.
Lemon tree borer on Research Area fence © Allison Buchan.
I wondered how big lemon tree borers could grow. I was puzzled when none of the reference sources I consulted said they exceeded 25 millimetres in length, but Ricardo Palma, curator of insects at Te Papa Tongarewa / The Museum of New Zealand told me that they are 'extremely variable in size' and I had photographed an 'exceptionally large lemon tree borer!' Te Papa has a collection of about 100 specimens in which the smallest is just 12 millimetres in length and the largest 28 millimetres. He would like to add an even larger specimen to the collection, so if you come across one of 30 millimetres or more you might consider donating it to Te Papa.
Fruits of the Forest
Autumn is a time when many trees are ripening the fruit that resulted from the pollination of spring or summer flowers. Brightly coloured fleshy fruits are designed to attract the eye and tempt the appetite of birds that will digest the fleshy part and excrete the seeds in many different places. With one exception, these photographs were taken while walking the 'red route' circuit in the lower valley and I realise that when it came to pointing the camera, like the birds, I was usually attracted by colour.
Ripe and unripe karamu fruit.
Karamu (Coprosma robusta). Ripe orange fruits started to appear in February and there are still plenty to satisfy hungry birds as April draws to a close. Because this is a dioecious species in which some trees are male and others are female, all trees are not capable of bearing fruit, only the female ones. The individual fruits in a cluster ripen at different times so newly ripened fruit is continually becoming available over a prolonged period. Individual trees also vary greatly in the time they start to ripen their fruit. As the season wears on some will have little or no fruit remaining, but others will be at their peak or just beginning. As a result karamu fruit is usually available for 5 or 6 months of the year. These characteristics ensure efficient seed dispersal for the karamu because there is not a sudden glut of ripe fruit that overwhelms demand and results in a lot going to waste.
These are some places to look for fruiting karamu as you walk along Lake Road: on the left at the junction with the Valley View Track (look up, this one is quite tall); opposite the entrance to Alison Morton's memorial; on the right beside bait station 14.
Ripe ngaio fruit.
Ngaio (Myoporum laetum). Ripe fruit was most abundant in March when I often saw tui and sometimes hihi eating it. Although birds can apparently digest it safely, the fruit is not suitable for human consumption because it contains a poison, called ngaione, which is harmful to the human liver. Fortunately the small size and unpleasant taste means that people are unlikely to be tempted by it. The fruit is usually not as exposed as shown in the picture. This particular tree, which I noticed on 23 March when walking between the Campbell St emergency exit and the Weka Fence on the inner perimeter track, did not have a well developed leafy canopy and may have been under stress. Elsewhere, including in front of the Lake Road toilets, thicker foliage made the presence of fruit less obvious.
Ripening pate fruit.
Pate / Patete / Seven-finger (Schefflera digitata). Fruit-clad fingers extend invitingly from a branch. The fruits are quite tiny but concentrating them on these finger-like structures makes it easier for birds to find them and have a meal without expending too much energy. As they ripen, pate fruits change colour from pale green through white and purplish pink to dark purple. These were photographed in late April on a tree above Te Mahanga Track about 22 paces south of the Weka Fence gate. Another place to look for fruit is opposite Birdsong Gully. The trees there ripen their fruit a bit later and their 'fruit fingers' droop more elegantly.
A ripe totara fruit has fallen.
Totara (Podocarpus totara). The presence of ripe fruit was revealed on 19 April when a few were spotted on the ground beneath the two large female trees on either side of the Jim & Eve Lynch Track. Like karamu, totara are dioecious. (The southernmost totara beside this track is assumed to be a male.) A sudden forceful shower of rain had probably been responsible for dislodging the fallen fruits.
A totara seed is not hidden in a fleshy wrapper but sits on a colourful succulent cushion called an aril. Actually swollen stems connecting the small green seeds to the tree, arils are a sought-after food for birds. When they swallow them, the attached seeds come along for the ride through the digestive tract. Falling down underneath the parent tree instead is not a good outcome, but if this seed is lucky some bird foraging on the ground will snap it up to get the aril and it will be on its way to a more promising destination where it can put down roots and grow.
Ripe kohia fruit.
Kohia / New Zealand passion vine (Passiflora tetrandra). In late April the ripe fruits were brightening up the bush on the far side of the overflow channel that runs alongside the access way from Waiapu Road to the Sanctuary entrance. Enjoy the sight while you can because the vine (or vines) will have to be removed to make way for the construction of our new Visitor Centre. Although seedlings for planting inside Karori Sanctuary have been raised from fruit collected at this site last year, it will be many years before they are capable of producing an equivalent display.
Tarata seed capsules ripening.
Tarata / Lemonwood (Pittosporum eugenioides). Unlike the other species listed above, tarata has seed capsules not fleshy fruits. The capsules persist in their green state for a long time. A change from bright green to a yellowish colour is the first indication that the ripening process is underway. Then the capsules darken to black relatively quickly. A week after these were photographed on 22 April, almost every capsule in the bunch was black. As the capsules dry out they become textured with minute wrinkles. Finally they split in two and gape open. Inside, a papery covering shields a clump of sticky black seeds. The number of seeds per capsule varies greatly. I have seen as few as two and as many as nine. Two generations of capsules, one recently ripened, one still green, are easily seen on the tarata growing on the north side of Round Lawn behind the Busby Family seat.
Tiny Tigers of the Insect World
There are no fierce furry felines to menace visitors in the Karori Sanctuary, but we do have colonies of common tiger beetles (Cicindela tuberculata). They are carnivores too, but they are very small (body length about 10 mm) and prey only on other insects. Humans are perfectly safe.
Tiger beetles are active during the daytime and on warm sunny days during summer and early autumn are often to be seen on clay patches on the Raingauge Spur Track. It is their quick movements that catch the eye but whenever they stop they seem to vanish. Those pale Art Nouveau style designs on their wing covers (which may have contributed to the 'tiger' name) seem to have a camouflage effect.
Common tiger beetles mating © Allison Buchan.
When I notice these tiny tigers racing madly about and making occasional short flights I assume they are hunting for their next meal. Their strategy is to run their prey down and in that respect they are more like cheetahs than tigers. However, when I spent some time watching for a photo opportunity one day in early March, I found that sex not food was the main preoccupation that afternoon. It was like a miniature French farce. Potential ladyloves were being pursued, eager suitors were being led on, unsuitable ones were being evaded, rivals were being seen off the premises, and it was all happening in fast forward mode. I had to give up trying to photograph a single tiger beetle as originally intended. They were always running at full tilt. But when a lady accepted a proposal there was a long pause during which I could photograph two at once.
Fruits of the Underworld
Autumn rains bring forth the fruit-bodies of fungi that for most of the year lead hidden lives in soil, leaf litter, or wood. The shapes and colours of these fungal reproductive organs are many and varied according to the species they serve but all have emerged to produce and disperse spores so that another generation of fungi can colonise new sites.
A crowd of Galerina toadstools.
Galerina species. These small pale greyish-brown toadstools with fluted cloche caps have no common name. This was just part of quite a carpet of them that appeared in mid April not far from the northernmost totara on the Jim and Eve Lynch Track. They were about 40 millimetres in height with caps 10-15 millimetres in diameter held aloft on slender stems. The spores are shed from gills underneath the cap and once that has been accomplished the toadstools can disappear remarkably quickly. I photographed these on 19 April and when I walked that way again only three days later they had all completely vanished, just as if the toadstool carpet had magically flown away.
The pores are on the undersides of the orange fruit-bodies.
Orange pore fungi (Favolaschia calocera) are probably the most asked about fungi in the Karori Sanctuary because their vivid orange fruit-bodies inevitably catch the eye. An impressive display hosted by a log lying on the east side of Te Mahanga Track, about opposite Botanical Trail post 7, was attracting comment in late April and will hopefully remain visible for a while. If that has faded, there will be others making an appearance elsewhere.
Among the dark shadows of the forest floor the colour is at its most intense and almost seems to glow. If you take the fungus out into the sunlight, the colour is much less bright. The caps are between 10 and 30 millimetres across and have a slightly bubbled upper surface. Underneath the caps, spores are shed from pores instead of gills. I turned a stick over to expose the pores for the photograph. You will find more about orange pore fungi in our Mid to Late Autumn 2006 edition.
Fruit-bodies of a wine glass fungus.
Wine glass fungi (Podoscypha petalodes). A remnant of a large woody tree root encroaching onto the Round the Lake Track (about 16 paces west of the junction with the Turbine Track) has been providing food and shelter for one of these, its presence unsuspected until the need to reproduce brought its fruit-bodies out into the open. When photographed on 22 April the delicate papery funnels with ruffled rims were looking somewhat battered so I don't know whether they will last much longer. These ones were up to 30 millimetres tall and the largest were 20 millimetres across but they can be twice that size.
For pictures of some other species of fungi that may be encountered in the Sanctuary see 'Ghost Dung, Earthstars and other Curiosities' in our Winter to Early Spring 2006 edition.
Kereru Observer
Kereru eating karewao / supplejack leaves Photo by Tom Lynch.
In 2006 our Mid to Late Summer edition featured Valiant, the first kereru / New Zealand pigeon (Hemiphaga novaeseelandiae) known to have hatched and fledged in the Karori Sanctuary. Although our conservation officers record any kereru activity they observe which may be an indication of breeding in the Sanctuary, there is no regular monitoring programme for kereru so we don't know whether any fledged here in 2007. However, we can confirm that one did in summer 2008. Karori Sanctuary conservation officer Matu Booth discovered the nest and all quotations in the following account are his words.
Karewao / Supplejack fruit is a convenient snack but more nutritious fruits are preferred.
The first clue that there might be a kereru nest planned or under construction at a particular site came on 9 November 2007 when, says Matu, 'a pair was observed just above head height on the Faultline Track close to the site. On that occasion the male broke off a twig before letting it fall to the ground. When they flew from the area the male performed a shallow stalled dive — all very suspicious.' Kereru had also been seen perching around the same part of the track during the previous breeding season. It was obviously a site meriting thorough investigation and on 25 November Matu succeeded in locating a nest where a kereru was already sitting on an egg.
'The nest was a small platform of sticks in supplejack which was scrambled though mahoe. It looked ridiculously small under the incubating bird and would have been about 50 millimetres deep,' Matu recalls. 'Although it looked like a precarious nursery space, I noticed that when the wind blew though the canopy, the platform remained quite still. The beauty of the nest from the observer's perspective was that it was only about 4 metres east of the track and at an easily visible height.' However, you did need to know just where to look. The nest was quite well concealed and unlikely to be noticed by casual passers-by.
Kereru parent feeding chick at the Faultline nest, 9 January 2008 Photo by Tom Lynch.
'One of the concerns through the incubation and nestling stage was that the nest seemed to get smaller and smaller as time went by. Kereru have a reputation for losing eggs from their nests and each time this nest was checked there was a moment of breath holding till a movement could be confirmed in the nest. By the end of the nest's life it looked like a small flat plate underneath the adult (and later the fledgling) which seemed to extend in every direction beyond it.'
The chick was first sighted on 20 December. A kereru chick doesn't have to jostle with brothers and sisters for parental attention. It is always the only chick in the nest. Just as well when the nests are so minimalist and the chicks grow into particularly large fledglings. This photograph shows the Faultline chick being fed. Both parents feed their chick, initially with a milky secretion from their crops, then with regurgitated fruit pulp and finally with regurgitated whole fruits.
Kereru perched in a kowhai tree.
The chick fledged sometime in late January. 'It was seen perching a short distance from the nest for a couple of days. Its colour was duller than an adult bird's and it had a wispy finish to its plumage which indicated that the transition from down to feathers was still happening.' That was the last definite sighting but we hope it is still somewhere in the Sanctuary and doing well. It is not practical to put the usual coloured leg-bands on kereru for future identification because feathering on the legs conceals them. Sometimes coloured strips called jesses are attached, but in this case it was better not to interfere. An attempt to get access to the nest might have collapsed the precarious structure altogether.
Although the outcome is unknown, the behaviour of two other kereru pairs suggested they were nesting in the Sanctuary. Here is Matu's description of activity at a Te Mahanga Track site. 'An adult bird was seen carrying a nest twig up into a dense tangle of supplejack on 15 December 2007 …[and] birds were seen to be active around the site over a considerable period. On the one occasion that I observed the adult accessing the site it was quite a mission as the bird swooped in at a level lower than the suspected nest and then squeezed and scrambled its way up though the supplejack.' It was then totally concealed from any observer down below. This illustrates how difficult it can be to find kereru nests, let alone observe them. They seem such obvious birds with their big bodies and noisy wings but invading their privacy is not as easy as one would think.
This edition of Nature’s Corner was written by Karori Sanctuary volunteer Allison Buchan in late April 2008. Hihi Herald is based on information supplied by Ron Goudswaard and Matu Booth's observations are extensively quoted in Kereru Observer. Both are Karori Sanctuary conservation officers. Unless otherwise indicated, photographs are taken by Allison Buchan and are © Karori Wildlife Sanctuary. Clicking on photos will take you to a larger version.