34 N.l. ECOLOGICAL SOCIETY

Some Notes on the Sea- and Shore-Birds of the Inner Hauraki Gulf

R. B. Sibson

The narrow isthmus on which Auckland catcher (Haemutopus reischeki) now nest- stands, deeply penetrated by creeks and in- ing within fifty miles of Auckland are very lets, and the inner Hauraki Gulf with its small but a few breeding pairs linger on many islands and estuaries, are frequented quiet stretches of beach. Otherwise the by great numbers of shore-birds and sea- life of the coast remains rich. Some species, birds, both for breeding and feeding. The notably black-backed and red-bi1led gulls, region under discussion is situated-between the pied and probably the white-faced other areas which are well-known for the heron have benefitted from pakeha civilisa- richness of their bird life. Manukau Har- tion. By scavenging on man's waste the gulls bour, to the south-west, and the Firth of appear to be surviving the winter in greater Thames, to the south-east, are unrivalled in numbers than formerly. Even so there is for the number and variety of still a heavy mortality of young black-backed () which feed on gulls in their first autumn, many evidently the eutrophic ooze of their tidal flats. To dying of starvation when left to fend for the north are the numerous outer islands themselves. Despite scavenging, the popula- of the Hauraki Gulf on which besides pen- tion seems to have. outstripped the food guins, gulls, terns, shags and gannets, twelve supply. Before the coming of the pakeha the species of petrels (Procellariifonnes), some eggs of gulls and terns from colonies on in immense numbers, are known to breed. easily accessible rocks were taken by moa- This is a remarkable concentration for so hunter and Maori and certainly were an im- small an area of ocean and indicative of portant item in their diet. The eggs and waters rich in plankton. Many birds from young of the gannet were also taken, so that these areas habitually forage in the inner man was a controlling factor in the popula- Hauraki Gulf; and under the stress of tion of these birds. With. the coming of pro- weather even the more oceanic petrels and tection these birds appear to have recovered shearwaters may enter Rangitoto Channel their former numbers and with some species or Tamaki Strait. For example, driven by a indeed the population may be at saturation summer gale from the north-east fle"h-footed point. shearwaters have been noted, somewhat in- congruously flying over the suburbs of the The white-fronted tern (Sterna striata), isthmus from the Pacific to the Tasman. of which the population runs into many thousands, is by far the commonest of the Man too has found the isthmus with its sea-birds which breed around the Waite- productive climate and fertile soil an ideal mata and on the inner islands. The numbers habitat, so that now this narrow strip of decline in winter, when tII,my are in south- land carries a population of 400,000. Urban- e;>st , as has Qeen shown by ring- isation has inevitably reduced the numbers ing. Though few C;>"pian terns (Hydro- of some species which once bred in swamps, progne caspia) breed in our area, hundreds on crater lakes and on the beaches or, like move in while the. breeding season else- the gray-faced petrel, on headlands and cliff- where is finishing,and stay over the winter. tops. The brown teal (Anas chlorotis) has Ringing has proved that somtj of these birds gone completely. The numbers of banded come from farther north, e.g. Kaipara; but dotterel (charadrius bicinctus), red-breasted one first-year;' bird which was recently re- dotterel (c. obscurus) and variable oyster- covered, bore a ring which had been put on N.Z. ECOLOGICAL SOCIETY 35 at Palliser Spit. The majority of local black- throated and white-bellied phases are well backed gulls (Larus dominicanus) come represented in this colony. As a general rule, from a large colony estimated at 1500 pairs, like pairs with like, but occasionally ob- which is situated on the lower western vious 'hybrids' are seen at the colony. In slopes of Rangitoto. Small numbers of red- winter, flocks of little black shags appear billed gulls (Larus scopulinus) breed around on Orakei Basin and in the shallow waters the inner islands. A great post-nuptial influx of estuaries, where they round up fish by is well on the way by the end of January. the mass-diving tactics which are character- In mid-winter the numbers in upper Manu- istic of this species. Persecution has made kau alone may exceed 20,000. Some of these the black shag (P. carbo) rather secretive move south from the great colonies at the about its nesting; but it remains common, Three Kings and Mokohinau. Ringing may and an autumn influx indicates successful prove that others have a southerly origin. breeding somewhere. At the Noises and Only three petrels breed within the limits around the north-east corner of Waiheke of our area, none of them in large numbers. there are thriving colonies of spotted shags Gray-faced petrels (Pterodroma macrop- (Stictocarbo punctatus), a more southerly tera), the mutton-birds of the north, barely species, here at the northern limit of its survive as breeders on the"mainland, but a range. few pairs still occupy some of the less acces- sible islets. They are winter-breeders, and During recent years at least twenty species are present in New Zealand waters through- of arctic waders have been recorded near out the year, though seldom seen close in- Auckland. Half of these may be expected shore. annually. The remainder are occasional stragglers, but wider coverage by an increas- White-faced storm petrels (Pelagodroma ing number of critical observers has proved marina) which reappear offshore in August that several arctic waders reach New Zea- continue to breed at the Noises. Where they land much more frequently than was form- spend the winter is unknown, but it may be erly suspected. The most numerous are in in warmer waters well to the north of New order of abundance: bar-tailed godwit, knot, Zealand. A few diving petrels (Pelecanoides turnstone, Pacific golden plover, sharp-tailed urinatrix) may still attempt to breed 'on the sandpiper, red-necked stint. Also small num- islets just off the north coast of Waiheke. bers of long-billed curlew, whimbrel, cur- Though the migrations of petrels are out- . lew sandpiper, and pectoral sandpiper pro- side the scope of this essay, it is perhaps bably occur as annual migrants. The tidal worth mentioning that a few giant petrels flats of the Auckland isthmus are also the (Macronectes gigalzteus) summer in the northern terminus of thousands of pied oy- Hauraki Gulf and winter numbers in Waite- stercatchers, pied and wrybills, which mata seem to reach a peak in August or after breeding start to leave the South Island September. " about Christmas and the New Year. Though wrybills breed in the South Island-actually Five species of shags nest near Auck- within a remarkably limited area--they land. Pied shags ( P. varius) usually spend eight or nine months of the year ii, choose to nest in trees which are growing the north. Flocks of banded dotterels whIch out from vertical sea-cliffs. While there are winter near Auckland may also partly ori- typical colonies on the islands, an excep- ginate in the South Island. Even during the tional colony has now flourished for seven summer, flocks of S.l. pied oystercatchers years on Lake Pl1puke. Here breeding goes (H. finschi) and wrybills (Anarh)'l1chus on continually, the nests being in exotic frontalis) remain. These flocks are composed trees which are growing out of the water of non-breeding juveniles. The evidence around the 'edge of the lake. Pied shags seems to indicate that these two species do from Waitemata often fly over the isthmus not breed till their second or third vcars. to feed in upper Manukau. The shaggery on The same is true of pied stilts (H. iel!co- L: Pupuke is mixed and also includes a few cephalus) of which non-breeding flocks are pairs of the elusive little black shaw (P. always present during the breeding season. su/cirostris) and many little shags ( P. mela- The origin of these birds is unknown. They noleucos) a dimorphic species. Both white- are not bred locally and certainly come from 36 N.Z. ECO LOG ICAL SOCI ETY farther south; perhaps only from the Wai- century. To the south and north of the isth- kato or the volcanic plateau, possiblv - from mus, stilts now nest in damp paddocks the South Island. which once were swamps deep in raupo, flax and kahikatea. Breeding has now been re- There is a difference of something over ported even from Waiheke and Ponui. Since three hours between the Tasman and the pakeha ornithology began in, New Zealand Pacific tides. When the tides are very big, the banded dotterel has been considered the it is not unusual to see flocks of godwits and commonest in the country, but there knots flying across the isthmus. Thus, as are now solid grounds for believing that the the rising tide on one side drives them off pied stilt outnumbers it. A winter census in the banks, they are able to rest and feed 1959 showed that about 7000 stilts were pre- on the other side where the tide is falling. sent in Manukau alone, and the population These flights, as thousands of birds in long of the whole isthmus probably exceeded successive lines pass over 'Mt. Albert and 10,000. The remarks of Sir Walter Buller on Avondale or Otahuhu and Papatoetoc-.the the status of the pied stilt near Auckland. nar'row necks where tradition says the in the nineteenth century are of most inter- Maoris once 'portaged' their canoes-ca" be esting relevance. most impressive. These flights are most noticeable in February and March when god- Since the first white-faced heron was re- wits and knots reach peak numbers near ported near Auckland in 1948, the success Auckland; for the isthmus serves as a fun- of'this enterprising species in occupying an nel through which many northbound :nigra- empty ecological niche has been nothing less tory waders, some of which may have sum- than phenomenal. The bird is now breeding mered as far south as Foveaux Strait, must freely where a decade ago it was unknown pass and where they pause before starting and winter flocks of more than twenty birds on the long oceanic flight to their arctic are not unusual in estuarine surroundings. breeding grounds. Less impressive but none White-faced herons have now spread to the the less characteristic of the isthmus are the inner islands where they will compete along daily foraging and roosting flights of the two the shore with the less adaptive blue reef common gulls. Shags of various species and heron (Egretta sacra). Another Australian Caspian terns may often be seen in the sky bird, the coot (Fu/ica atra) appears to be over Auckland. increasing rapidly in the South Island. It A few white herons (Egretta alba) pre- will be interesting to see if coots which have sumably from Okarito usually winter near been present on L. Pupuke for more than a Auckland appearing in April or May and de- year are the forerunners of another suc-' parting in the spring. The numbers in 1957 cessful invasion. . and 1958 were exceptional and point to an irruption from Australia. White herons seen There is little precise information about near Auckland in summer must be 11011- the food of birds in New Zealand. This could be a worthwhile study. The interest of the breeding juveniles. During recent years problem is simply illustrated by the quite royal spoonbills (Platalea regia) have b,een different feeding habits of three species of occurring much more frequently. The bulk terns, which occur about the isthmus. of the breeding population from Okarito White-fronted terns range some miles out winters at the Manawatu estuary, but as the to sea and usually outnumber the other sea- numbers increase that estuary is proving too birds in the' swirls' which form over shoal- small to support them and royal spoon'.JilIs ing fish. The other birds of the swirls may are regularly wintering in northern New be gannets, shearwaters of two or three Zealand. Non-breeders have been present. species, red-billed gulls, a few black-backed near Auckland during the last two summers. gulls, the odd giant petrel, '}nd, clepto-para- If these royal spoonbills are not Okarito- sitic on the terns, some Arctic skuas (Ster- born, they must be invaders from Australia. corarius parasiticus). Caspian terns find Pied stilts and white-faced herons (Ardea most of their food in the tidal shallows and novae-hollandiae) are examples of birds up the creeks which small numbers of white- which by swift and vigorous colonising, have fronted terns may penetrate mostly in increased most conspicuously in the last half autumn. Caspian terns also readily visit - N.Z. ECOLOGICAL SOCIETY 37

coastal lagoons and freshwater lakes. These which may deserve more detailed treatment are the true hunting-ground of the white- will receive but scant mention. The harrier, winged black tern (chlidol1ias leucopterus) kingfisher, pipit and fern bird are examples which is predominantly an insect-eater and of eurytopic species which may breed not therefore does little foraging over salt water. only on the saltings or seacliffs of the isth- A three-acre pool of flood-water over grass- mus, but also far inland into the hills and 'land has sustained one of these marsh terns mountains. The pipit perhaps has the great- over an Auckland winter. Another example est altitudinal breeding-range of any New is provided by the larger waders. The feed- Zealand bird, but some black-backed gulls ing habits and habitats of oystercatchers, have deserted the coast for breeding and stilts and godwits seem to indicate that now nest high in the Southern Alps. In while there is some overlap in their diets, winter especially, mixed flocks of the intro- each species has its own preferences from duced finches and buntings which have done the varied menu of the tide-line. so well in New Zealand, occur commonly on the coast. The use of the sea-shore and In a general survey such as this, there the saltmarsh by these birds is a study in will be inevitable omissions and some topics itself.

SUMMARY

TYPE OF HABl'rAT: EXAMPLES: DRl':p;mNG Dmns: FgF,DTNG HmDs:

Freshwater Lake L. Pupuke Pied Shag, Little Black Shag', Sha.,ms (4 species) We."Item Springs Little Shag (both phases), Bit. Bibtem, White Heron, 'Vhite-faced Heron tern, Gray Duck, l)ukeko, ('Big Gray Duck, Pukeko, Caspian Tern, Coot ,Black Shag) (v. rare).

:Muddy creek with 'Vhau, Banded Rail Gannet, ShagI'! (4 ~peci('fl) mangroves Purewa, 'Vhite Heron 'ramaki, Hande-(! Rail Turanga, \Vrybill (in autumn) \Vairoa Oaspian Tern (at all soosons) White-fronted Tern (in autumn) Saltmarsh & sh-al1ow Estuarie.<; of Bandoo Rail Bittern (in autumn), White-faced Heron lagoons wivh salioor- Whau, Tamaki, Gray Duck Gray Duck, Banded Rail nia, stlJllolus, plag'i- Turanga, Wairoa Pied Stilt, White-wingoo Black nnthus, etc. Tern (oec.) Ca.~pian Tern. Tidal flats with sandy l'~tuariffi of Banded & Hed-bre

Offshore walters: Noioos Lit.t,le Blue Penguin, Grey-fMed Little Blue Penguin, Pell:rels (as. a.hove) -outer islelts be)'Dud HQfUhoru Petrel, Wh.ite-faced Storm Peirel, with Buller ',s Shoo..rwruter & Cook's Pet- .,Waiheke & Rangitoto 1~M"rukiihl Diving Petrel, Gannet, Spotted & rel (summer), and B1ack-browed & Sal- Pied Sha.g, White-fronted Tern, vin ',g Mollymawk (winter), Gannet, Spot- Reef Heron. ted Shag, Red.billed Gull, Whit-e-frontoo 1'ern, Arctic Skua.