Kotuku (White Heron) of the Waitangi Roto

Bird of a Single Flight

“About six miles up the river branched in many small arms, and my progress was put to an end by large trees lying across.  Dense bush on both sides of the river, the beautiful kowhai trees abounding and almost all shrubs in flower made this a real pleasure trip. But the crowning beauty was a cranery which I discovered up the river, and that was a glorious sight...   Imagine seeing around you from 50 to 60 (of these birds) sitting on high pines and lower trees in a circle of about 150 yards, their pure white feathers shining in the sun...   They were not at all shy (and) kept up a continual “plappering" among themselves and seemed to be astonished at me more than afraid... ”

"Gerhard Mueller, first District Surveyor for South Westland, encamped at the mouth of the Waitangitaona River on New Year’s Eve, 1865."

Kotuku or White Heron

In shallow waters throughout New Zealand, near the edge of estuaries, harbours, lakes, ponds and along the banks of rivers and streams, from the end of summer to the beginning of spring, you may, if you are lucky, chance upon a solitary large, white, long-necked bird, stalking the shallow waters. This is Egretta alba modesta, the kotuku or white heron, a common enough wader in many parts of Australia, the South Pacific, tropical Asia and Japan, but one that seems always to have been rare in more temperate New Zealand where the present population is about 80 breeding adults and 50-60 first and second year birds. To the Maori it was “He kotuku rerenga tahi”, a kotuku “of a single flight”, a kotuku to be seen perhaps once in a lifetime.  As a symbol of things both beautiful and rare it occupied an important place in their myth and folklore, and to compare a visitor to a kotuku was a compliment of the highest order.  In the more tangible world kotuku plumes were sought and treasured by people of high rank, though the longest and most valuable were tapu and forbidden to be worn by women.

This beautiful bird breeds only in a single secret location in what is one of the most romantic parts of the country. The continued survival of white herons has been one of the major successes of the early stages of wildlife conservation in New Zealand, bearing in mind that had they been an endemic bird they would long have been on the “critically endangered” list.

The Waitangiroto Colony

In August and September white herons begin arriving at the Waitangiroto colony. During this time they undergo striking changes. Long, white, loose breeding plumes develop on the back and wings, the yellow bill turns dull black, and the facial skin between the eye and bill brightens to a bluish-green. Pairing off is a time of elaborate displays and rituals with plenty of noise and action as opportunists try their chance and squabbles break out. Eventually though between 30 and 40 pairs settle down on their platform nests, and by the time the tours begin in early November the first of the chicks should have appeared. From three to five blue-green eggs are laid, but usually only one or two chicks per nest are successfully reared.

Success in fledging chicks varies considerably from year to year. In the summer of 1981-82 a record 60 chicks were reared from 48 nests but the following summer only 21 chicks survived from almost the same number of nests (42). Storms during the early part of the nesting season are a significant factor in determining breeding success, hut the condition of the Okarito Lagoon, the herons’ main feeding ground, also plays a part. From time to time the outlet of this largest of a11 West Coast tidal estuaries gets blocked, and as water levels rise the lagoon becomes unsuitable for shallow water waders like the kotuku. When this occurs in the spring the disaster is com-pounded, since at this season large shoals of inanga (or whitebait) normally enter the rivers and lagoons of South Westland. And whitebait provide not only the chief focus for human attention in the region throughout September and October, but are also probably the principal food source of the nesting kotuku.

dendrobium,  Tree Orchid	Thelymitra Pulchella,  Native Orchid	pterostylis banksii, Hooded Orchid

Spoonbills and Shags

Two other birds which have a special relationship with the Waitangiroto heron colony are the distinctive royal spoonbill, Platalea leucordia regia, and the rather more ordinary little shag, Phalacrocorax melanoleucos.  Little shags are a common enough sight along rivers and streams throughout New Zealand, and since regular monitoring of the heron colony began in 1940 have nested in close company with the herons. Royal spoonbills on the other hand are very rare in New Zealand, and their nesting since 1951 along the same stretch of the Waitangiroto River as the white herons has been a real bonus for the sanctuary.

Like white herons royal spoonbills are widespread in Australia and were known to the Maori as kotuku ngutu papa, “the board-billed kotuku”. But only 6 spoonbill sightings were recorded in New Zealand prior to the 1930 when they began to be seen more regularly. Juveniles were first noted in New Zealand 1944, so breeding is assumed to have begun at about this time.  In the summer of 1949-50 a single pair of spoonbills bred alongside the white herons at Waitangiroto. In the following years others joined them, building up the colony to a peak by 1970. Through the 1970s little nesting occurred although spoonbills were present each spring. In the 1980s there have usually been a dozen or more nests but very limited success in fledging chicks. The reason for this is that at Waitangiroto spoonbills build their nests in the exposed canopy of the tallest kahikatea trees and regularly lose all their eggs or chicks in storms. At the end of the breeding season the spoonbills depart and become even more elusive than white herons, except on the estuary of the Manawatu River where a fair number of them seem to gather for the winter.

Royal Spoonbill, 
with it's “long-haired larrikin” look

From a visitor's point of view there is little doubt that their presence is a significant part of the local attraction. When you’ve spent an hour or so at the hide even the legendary kotuku begins to shed some of its "single flight” aura; but not so the spoonbills whose descents from their scattered canopy nests are infrequent enough to preserve their mystique.  Added to which is their outlandish appearance: a long, black, spoon shaped bill; a bare, black face and baleful, yellow eyelids; and long, drooping, breeding plumes on the back of the head, giving them a kind of “long-haired larrikin” look.

The Local Landscape

New Zealanders have long associated the white heron nesting colony with Okarito.  But although the herons feed extensively in the large Okarito lagoon the nesting site is in the next catchment to the north. In bygone days one might indeed have set out from Okarito to visit the colony, going by boat across the Okarito Lagoon, following the track over the Waitahi Bluff, and then making use of a second boat to go up the Waitangiroto River. Today however most visitors come from a different direction, and reach the colony by way of the outwash plain of the former Whataroa Glacier, first travelling by road and then by jet-boat down the Waitangitaona, the middle of three rivers of striking contrast which cross the Whataroa flood-plain.

Panoramic view of a valley near Whataroa*

Northernmost of these is the Whataroa, a typical, big, flood-prone, South Westland mountain river, draining a huge sector of the Main Divide. Freed at last from the con-fines of its mountain valley, the Whataroa weaves an ever-changing pattern of braided channels across a broad gravel bed as it moves swiftly to the sea. In the past these braided streams would have shifted back and forth across the whole of the lower “valley”, gradually constructing the present level floodplain between confining ridges of old lateral moraine.

 Wending a much more sedate course down the middle of this floodplain is the Waitangitaona. Not long ago this river drained a very much larger catchment, but its recent history is a good example of the kind of changes that can happen in dynamic landscapes like South Westland. During a major storm in 1967 the river changed course on leaving its sizeable mountain catchment, abandoning its former lowland channels and joining the sea 10km further south by way of Lake Wahapo, the Okarito River and the Okarito Lagoon. As is still obvious from the main highway, this change has had devastating consequences for a fine stand of kahikatea swamp forest at the head of Lake Wahapo, killing many of the trees by raising the watertable and inundating the forest floor with large quantities of gravels.

Mountain views on the road near Whataroa*

In contrast to the clear shoals of the Waitangitaona and the swift snow-fed waters of the Whataroa, the Waitangiroto meanders across the southern margins of the flood-plain, deep, sluggish, sinuous, stained by humus and overhung by forest. Although at present an ideal nesting site for the herons and shags their long-term tenure depends in part on the whims of the other two rivers, either of which could dramatically alter its character. Should, for example, the “upper” Waitangitaona abandon its new route and revert to its former course it could easily opt to combine with the Waitangiroto for the final stages of the journey. Or, in some cataclysmic flood, the Whataroa River itself could shift across to the southern side of the floodplain. Such an even occurred at the mouth of the Cook River in 1967, and devastated an area of kahikatea forest far greater than that at either Lake Wahapo or the Waitangiroto River.

 

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Photography by Ulrich Walthert, those with * by William Glendenning
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