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Nature’s Corner — Late Autumn to Winter 2008

Winter Reflections

Roto Kawau, the lower lake in Karori Sanctuary, resembled a mirror on the crisp but sunny, and unusually calm, morning of 15 July. Such intervals of beauty and restfulness were a welcome respite from the gloomy grey skies, cold showers and biting winds brought by the succession of cold fronts that dominated the month. The views are from the far end of the dam, near the large pipe that once delivered water from Kaitoke to this former city reservoir. The only clues to the season are some pale brown patches in the evergreen bush on the ridge that descends steeply to the water on the far right of the first picture. These are tangled mats of leafless stems, the temporarily exposed frameworks of winter-deciduous pohuehue vines.

I wonder how these scenes will look in another fifty years? The tall trees that are currently such a prominent feature on the eastern shore are Monterey or radiata pines (Pinus radiata) an exotic species that is native to California but extensively used in New Zealand for plantation forestry. Some pines are felled in the Sanctuary each winter. Our long-term goal is to replace them all with the kinds of native trees that grew on these hillsides before they were cleared in the 19th Century to provide farmland, timber for construction, and firewood. Eventually people will look across the lake to see a forest with a different profile. The emergent trees will be rata, matai, rimu and miro, providing not just perches for our native birds but essential foods like nectar or podocarp fruits.

Korimako Chronicle

The bellbirders made another lightning raid on Kapiti Island this July and kidnapped ten more females for the delectation of Karori's notorious bachelors. I refer of course to Karori Sanctuary's mateless male korimako / bellbirds(Anthornis melanura), whose plight has been canvassed in these pages before. To improve the status of our small resident population we need to get them suitably matched and breeding and that means building up the number of resident females.

In order to reconcile the latest consignment of bewildered brides to their fate I am told they were treated to several days restful holiday, all expenses paid and meals provided, in a rustic bush hideaway. I wonder if a certain TV dating programme inspired this strategy? A spy tells me they dined from the following luxury menu: 'pottles of sugar water; jam/honey water; one pottle of sultanas which had been steeped in warm water and left overnight; wombaroo; nectivore/insectivore mix; as well as two halves of ripe, fresh fruit a day.' I hope their expectations of life in the Sanctuary were not raised to unrealistic heights. Fortunately there are delicious natural nectars available in our winter bush from kotukutuku / tree fuchsia and other flowers.

Refreshed and well fortified, the ladies were released on 21 July to meet the not so gentle men. I was originally going to say 'gentlemen' but the following eyewitness account of korimako courtship changed my mind. On 1 August, a volunteer bird monitor was observing behaviour in the vicinity of a supplementary feeding station when she saw 'a male serenading his partner from last year. He sat close to her and sang — all fluffed up — and at the end of his wonderful song would reach forward and give her chest a resounding peck. This happened several times. Not the way to win a lady I would have thought!' Nor I, but there is no accounting for individual tastes. Perhaps she finds it stimulating.

The first sighting of one of the newly released females was made near another feeding station on 3 August. She was being serenaded by one of our bachelor males on that occasion and subsequent sightings of her in the area indicated she had decided to stay. On 22 August conservation officer Matt Robertson confirmed that so far three of the new Kapiti females had paired with Karori bred males, and one established pair and one of the new pairs had been observed carrying nesting material.

Matt finds it encouraging that the new pairings were made so early in the season. 'It is also pleasing to see three females that bred successfully last year return to their respective breeding areas,' he says. However the population 'is still critically vulnerable because of the low number of pairings due to poor recruitment of locally bred females.' New strategies are being tried in an effort to reverse that trend.

Flying Seeds

Toetoe(Cortaderia toetoe) is one of five New Zealand species of Cortaderia distinguished by botanists. All five share toetoe as their common name, although only this one gets to include the word in its scientific name. It was an overcast day in May, with a hesitant breeze, when I stopped to look at these seed plumes beside the road just south of Round Lawn. The rather stiff and erect shape of the plumes is quite usual for Cortaderia toetoe, whereas Cortaderia fulvida, the other toetoe that grows in Karori Sanctuary, has plumes that curve gracefully.

Toetoe and the related pampas grasses of South America depend on the wind to spread their seeds and furnish them with tufts of fine hairs to help them parachute away. Cortaderia fulvida flowers in spring and its seeds had departed, but Cortaderia toetoe flowers in summer (usually in January) and I was curious to see if their plumes still contained seeds in late autumn. They did, but they were in the process of liberating them. When I looked very closely I could see them being shaken free and flicked away on the breeze. In the picture the expanded parachute hairs catch the light and show up white, indicating the positions of the emerging seeds.

Here is the reason for those lofty plumes. (Held upside down, but you get the idea.) If you are going to parachute anywhere you need to jump from a height. Likewise, to hitch a ride on the wind you need a launch site with maximum exposure to it. I wonder where this carefully packaged seed ended up? Not in the lake I hope.

Winter Nudity

Pohuehue(Muehlenbeckia australis) is one of those plants that react to winter by casting aside their leaves. In other words, it is deciduous. Together with the kotukutuku / tree fuchsia, it is responsible for the brown patches that blot the predominantly evergreen canopy of Karori Sanctuary's regenerating bush each winter. That is the time, while it is nakedly obvious, to get an accurate picture of the proportion of pohuehue in the bush canopy before new foliage gradually blends it back into the surrounding greenery in spring.

Pohuehue vines climb over other trees and shrubs to claim a place in the sun. However they will make use of other props when necessary, as the green garland on our Ops Yard fence testifies. I imagine fence maintenance will decree its removal one day, but while it survives, it is very conveniently placed for viewing a pohuehue at close range and seeing the fine detail of flowers and fruit in season. In early May it was still fully clothed in green leaves and was ripening fruit. The fruit identified it as a female. Pohuehue are dioecious (having male or female flowers on separate plants). Male plants cannot bear fruit. Their contribution is producing the pollen that fertilizes female flowers. Without pollination, females cannot fruit either.

Fertilised flowers close their petals (tepals to botanists) while single three-lobed seeds develop inside. With its lime green covering, immature fruit is easily mistaken for flower buds. In the process of ripening, the sheltering petals swell up, turn a translucent white and gape open as the seed reaches maturity. The dark seed is ready for lift-off, but it is the sweet and succulent cup that causes a bird or lizard to ingest the seed and take it for a ride. The edible cup is its plane or train ticket to the future.

In June and July pohuehue are naked or nearly so. The one on the fence is only a few years old but some of those in the bush have built up an enormous infrastructure, creating mounds half a metre or more in height that are composed entirely of layer upon layer of intricately interlaced stems.

Foliage past its 'use by' date is not worth keeping but seeds are an investment in the future and not to be squandered. Female pohuehue retain and continue to ripen their fruit even in their leafless state. Those succulent little fruit cups continue to have a place on the bird menu throughout the winter. Tui, hihi, waxeyes and blackbirds are among the birds that eat them.

In August new leaves are becoming noticeable, dotted about sparsely at first on the tangled stems. Pohuehue are gradually reclothing. Leaves are the food manufacturers that will provide nourishment for a new season of growth. Soon growing shoots will be casting about for something more to climb. If there's nothing handy, they support themselves by mutual twining.

Some of our native Muehlenbeckia make attractive and interesting garden plants, but this one is seldom recommended. It is too vigorous and likely to become a nuisance unless you are a fanatical pruner. Who knows what it would get up to when you went on that extended holiday? It should be left in its natural habitats: native shrublands, regenerating bush and forest margins. As well as fruit snacks for birds and lizards, its wickerwork of stems provides nest sites and gecko hideouts, its flowers attract insects, and its leaves sustain kereru and pepe parariki / common copper butterfly caterpillars.

Kereru Observer

Kereru / New Zealand pigeons (Hemiphaga novaeseelandiae) have been regularly seen and heard in Karori Sanctuary this winter. A particular hotspot has been the section of Lake Road from the Kawau Lookout fence to the Kawau Point platform above the pontoon. The exotic Montpellier broom (Teline species or hybrid) growing on the steep hillside above the road has been furnishing them with salad greens. I have several times watched birds feeding there. One day I saw four. If they are perched side-on or with their backs to you, they blend into the foliage amazingly well, but if they are facing towards you that immaculate white shirtfront gives their position away. At this time of the year the large fruits that they favour are not available and they depend on leaf salads.

Another clue to the whereabouts of kereru in the broom is the quaking they cause when they shift position. The bushes have slender pliant branches and an adult kereru weighs about 650 grams. If part of a bush suddenly starts flapping about wildly, there is probably a kereru in there. Sometimes a crashing sound alerts you to their presence, usually the aftermath of a jump or short flight to a new perch, or sometimes an overloaded branch collapsing.

Flights in and out of the grazing area attract attention too because of the noisy swish of their wings. In the vicinity of the south end of the Kawau Lookout fence, there is a copse of native trees, mostly tarata / lemonwood, up on the bank. It overlooks the Montpellier brooms and often provides a handy perch for some kereru time-out. At other times the kereru retire higher up into the tall pines.

Kereru are not very vocal birds, but once what made me look up into the broom was a single soft 'ooooh'. After quite a long pause there was an answering 'ooooh' from another kereru also feeding in the bushes, so I presume it was a contact call from one spouse to another.

On 10 July Frances Gazley was returning down Lake Road when, in her own words 'I happened upon a kereru picking the tiny leaves from a broom just beside the video monitor on the Lake Road platform above the pontoon. When a second kereru landed by the first, it fell right through to the ground out of the small tree. It lumbered back up and carefully rejoined the first!' Either it had overshot its landing point or had miscalculated the ability of a branch to bear its weight. Maybe it was too busy looking for a reaction from its mate to notice where it was putting its feet.

The white flowered tree lucerne / tagasaste (Chamaecytisus palmensis) is another introduced plant growing wild in the Sanctuary that kereru find palatable. Both it and Montpellier broom belong to the same family as our native kowhai (Sophora species). Kowhai leaves have been a common food in late winter and early spring for generations of kereru and are still on the menu. During August kereru have occasionally been observed partaking of this traditional fare near the north end of the Jim and Eve Lynch Track and where the steps to the Discovery Area begin. So far the foreign fare seems to be winning the popularity contest though. It's nice that weeds can sometimes have a positive side.

For more about Montpellier broom refer to 'No, Not a Kowhai' in our Early to Mid Spring 2006 edition.

For more about kereru visit the Kereru Discovery Project website.

On the Botanical Trail

Perhaps you have noticed occasional wooden posts displaying numbers along Lake Road and Te Mahanga Track. These are markers for the Botanical Trail developed for the Karori Sanctuary by volunteers from the Wellington Botanical Society. The numbers relate to information in a trail guide published by the society and available from our Visitor Centre for just $1.

Get a copy as you enter and learn about the history of the vegetation in Karori Sanctuary and the characteristics of a selection of New Zealand plants growing here. During your walk you will find out how certain plants provide food for our birds and how some plants have been put to human use. If you want to be able to identify native plants but need some recognition practice before you can feel confident that you know a rewarewa from a kawakawa, taking the Botanical Trail will help you hone your skills.

Rewarewa (Knightia excelsa) are prominent in the regenerating bush on the western scarp, viewed at the first stop on the trail. They are the tall upright trees that stand out from the surrounding blanket of greenery like exclamation points. In winter most of them have racemes of flower buds developing. The photograph shows a single raceme, about 5.5 centimetres long. When fully grown it will be about 10 centimetres in length and may have as many as fifty to eighty tubular flower buds. The flowers usually open in November transforming the raceme into an impressive mass of curled crimson petals.

The photograph was taken from the Valley View Track where it runs alongside the Research Area fence. Stop by post 308 and look into the enclosure. Racemes of flower buds and clusters of empty seedpods are visible on the tree there. A rewarewa leaning across the stream at the bridge near Botanical Trail post 16 on Te Mahanga Track will probably produce flower buds in spring. Its shady location holds it back.

Winter Sweets for Nectar Lovers

Kohekohe(Dysoxylum spectabile) was flowering on the western scarp from May to July. While the nectar was flowing the bush rang with the signature songs and alarm calls of korimako / bellbirds and tui as they tried to claim exclusive rights and disputed ownership of the resource. In late July the ground was littered with long yellowish-green stems, some with flowers still attached, brought down by boisterous winds. The photograph shows a flowering stem on a fallen leaf. Such stems don't sprout from amongst the foliage but droop from the bare branches beneath and from the trunk. Kohekohe has large compound leaves, each consisting of 3-4 pairs of leaflets on a stem with another leaflet at the tip.

Kotukutuku / tree fuchsia (Fuchsia excorticata) in winter may look bare and lifeless or have the merest hint of returning foliage but close inspection usually reveals buds and flowers and even green fruit in July and August. I saw flowers in May and June too but only on a few trees and quite sparse. 'Looking into Kotukutuku flowers' in our Winter to Early Spring 2006 edition explained that some trees have hermaphrodite flowers and some have female flowers. At Tui Terrace I was intrigued to discover that the young tree growing by the pine log had three branches with hermaphrodite flowers but female flowers on all other branches. Then I saw that the three odd branches were not visibly joined to the rest but disappeared into the soil. I suspect some seeds germinated close together and what looks at first like one tree is actually two or three.

The photograph shows the difference between female and hermaphrodite flowers. Colour has nothing to do with it. Both types of flower are green and purple while they are producing nectar, changing to pink then red once they have ceased, a colour code that nectar-eating birds quickly learn and exploit. Look instead at comparative size and stamens. The female flowers are the smaller ones with stamens barely showing. The larger hermaphrodite flowers have prominent stamens and only they can produce pollen, which as you can see is blue. Did you notice in 'Korimako Chronicle' above that the bird taking nectar from a hermaphrodite flower has had pollen dabbed on his head? He doesn't know it, but he has been recruited as a kotukutuku pollinator.

Whauwhaupaku / Houhou / Five-finger (Pseudopanax arboreus) seemed to flower a little later than in previous years, with the first flowers opening during the first week of July instead of the last weeks of June. As explained in 'Looking into Whauwhaupaku flowers' in our Early to Late Winter 2007 edition, these trees are predominantly dioecious. Male flowers are pictured here. Notice the all-important pollen-shedding stamens radiating from each flower. When taking the photograph I brushed another flower mass with the crown of my navy hat and came away with a very intricate pattern imprinted in pollen. I felt obliged to fulfil the delegated role of pollinator and shake my hat over the flowers of a nearby female tree. Tui, korimako / bellbirds, hihi and tauhou / waxeyes harvest nectar from the male flowers, but don't seem to utilise the smaller female flowers. Whiteheads visit male and female flowers but are targeting the insects they attract and little spiders that hang out there.

Signs of Spring

Kowhai (Sophora microphylla) seen from the stairs to the Discovery Area and the Jim and Eve Lynch Track have tiny golden brown flower buds in August although you may need binoculars to distinguish them. Those big old trees, which pre-date the establishment of Karori Sanctuary, usually start flowering in mid to late September. Some young kowhai in lower valley plantings are further ahead, presumably the result of more northerly and warmer locations, or possibly a different genetic heritage in some cases. One midget beside Lake Road just the north of the toilet block had two flowers open by 20 August and other buds showing colour. No need for binoculars here, instead you may need to bend over for a closer look.

Puawananga (Clematis paniculata) flowers have been visible since mid August in neighbouring Birdwood Reserve. You can see them from Waiapu Road when walking between our office and the Visitor Centre. Keep an eye out for more constellations of their starry flowers when walking in the Sanctuary, especially when looking across to the western scarp. I noticed one on a rewarewa across the lake when standing at the mesh safety fence just south of Round Lawn. Sensitive leaf stalks that coil around branches and twigs they touch, allow puawananga and other Clematis to climb to sunny perches where their flowers can develop.

Tree Weta Tribulations

Putangatanga / Taepo or Taipo / Wellington tree weta(Hemideina crassidens).

If you have visited Karori Sanctuary, you have probably viewed these fearsome-looking relatives of grasshoppers and crickets through the Perspex windows of weta hotels as they slept the day away oblivious of human scrutiny. This is a benign and pleasant alternative to unexpected encounters in the field, which can be uncomfortable for humans and dangerous to weta.

People often find these big insects quite scary, but think how terrifying we giant beings must appear to them. A human can easily kill or maim a weta by stepping on it or handling it roughly, but I have not heard of a human being seriously damaged by a weta. The most they can do is nip or scratch and that is only in self-defence when imperilled by your close contact. Don't touch them and they won't touch you. To scare off predators they raise their spiny back legs in the air. They don't want a confrontation any more than you do, and will move away if you leave them an escape route. Accidents happen of course when you don't see them until it's too late. Some words of advice: Don't leave your footwear outside overnight and avoid poking unprotected fingers or hands into tree holes or similar confined spaces when you cannot see the interior.

The spirit of scientific enquiry sometimes demands that you delve into places that you would ordinarily rather not. Bird monitoring is not the gentle and refined leisure activity you may imagine dear reader. You have to be hardy, energetic, and prepared to get clothes torn and dirty as you force your way into thickets and slide down steep slopes in undignified positions in order to collect data on our feathered fauna. You must also be ready to take on occasional unsavoury tasks such as cleaning out last season's nesting debris from hihi nest-boxes in preparation for the new breeding season.

A volunteer bird monitor who was engaged in this chore at the beginning of August, reports that the job 'requires gardening gloves as often, hidden under the base twig foundation, can be tree weta of various sizes. A hearty nip is an unpleasant greeting! I try to encourage them out the nest-box hole, where some hang by only one leg before clambering to a nearby branch or dropping to the ground. I had five in one box the other day — two large females and three smaller ones. A robin searching the ground underneath the nest-box probably scored an unexpected, crunchy treat! The robins remove both the legs and head and eat just the striped body of the weta.' An untimely end for the weta is a banquet for a hungry bird, but that is life (and death) in the food chain.

This edition of Nature’s Corner was written by Karori Sanctuary volunteer Allison Buchan in late August 2008. Korimako Chronicle includes information supplied by Sanctuary conservation officer Matt Robertson. Thank you to fellow volunteer Frances Gazley for sharing her observations of various species. Unless otherwise indicated, photographs are taken by Allison Buchan and are © Karori Sanctuary. Clicking on photos will take you to a larger version.

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