34 N.l. ECOLOGICAL SOCIETY Some Notes on the Sea-Birds 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 bird 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 stilt 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 New Zealand for the number and variety of still a heavy mortality of young black-backed waders (charadriiformes) 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 Australia, 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 stilts 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 wader 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.