Physical Environment
The coastline from Cape Brett to Taiharuru Head is basically comprised of steep eroding cliffs and associated inter-tidal reefs. While small beaches occur in many embayments, there are few beaches relative to the length of the coast. However, the open coastline is varied, consisting of headlands, beaches, cliffs, reefs, stacks and small islands. These features combine to modify the winds, waves and currents, thus creating a huge variety in the shoreline and sub-tidal conditions over small areas.
This coastline is a classic example of a “submerged” coast. When the sea level rose after the last ice age it drowned existing valleys, and created headlands and islands from outer ridges and hills. Since then, wave action has tended to straighten the open coastline by cutting back cliff headlands and islands, and by filling in the indentations with sand or shingle. Contrasting with the predominantly exposed conditions on the open coast, are the more sheltered harbours of Whangamumu, Whangaruru, and Tutukaka, and the estuarine areas at Matapouri Bay and associated with the Whananaki, Ngunguru, Pataua and Taiharuru Rivers. Fluvial erosion (i.e. erosion caused by rivers and streams) has been significant in shaping these estuarine areas (Hume & Herdendorf, 1988). The harbours are formed from submerged valleys. In some areas, such as Bland and Mimiwhangata Bays, coastal embayments have been shaped by a combination of stream erosion, wave erosion from the sea, and sub-aerial weathering (Hume & Herdendorf, 1988). Unlike more enclosed estuaries, these estuaries are only partially enclosed by rock headlands, allowing free connection with the sea.
The rock of the whole coastal area, including cliffs, shores and sub-tidal areas, is greywacke – varying from soft, weathered “brown rock”, to jointed siltstones or massive sandstones. Greywacke is common on the East Coast of Northland. It was deposited as fine sediment in a deep trench on the seabed about 200 million years ago. Subsequent earth movements have twisted and shattered the rock, resulting in a criss-cross pattern of jointing. Today the rock is cracked into very rough surfaces providing innumerable microhabitats for organisms in pools, crevices and crannies. Bare rock cliffs are found, but more commonly steep vegetated seaward slopes in excess of 40 degrees characterise this area.
The sediment types on the eastern coast of Northland have been determined by sampling of marine beaches and foredune sand and analysing their median grain size, mineralogical content, and the proportions of minerals present (Schofield, 1970). The sediment type on this coast is called the “Bay of Island Sand Facies”. This sediment type extends from the south of Doubtless Bay (north of the study area) to Ngunguru Bay, where it becomes mixed with the sediment group to the south, the “Hauraki (B) Sand Facies”.
A report by Applied Geology Associates (1982) describes the sediments: “ The Bay of Islands Sand Facies has a high rock fragment content compared to other facies (sediment types), with approximately equal bulk proportions of shingle, quartz and feldspar sand, and shell fragments. The sediment is largely derived from the greywacke coastal cliffs and rock platforms, with a small contribution of quartz sand from the north, and feldspar rich sand from the south. Extensive gravel deposits in 20m – 40m of water are older coastal deposits derived under conditions similar to those existing today during periods of lower sea level” .
In general, the larger beaches on this coastline are light coloured and are composed of sands with a higher proportion of calcium carbonate than quartz and feldspar. Many of the smaller beaches are darker in colour and contain a high proportion of finely ground greywacke. In many places the sediment grain size varies considerably, with some layers being as large as to constitute fine gravel. Pockets of scattered layers of quite large pebbles are also common. At a few localities, beaches are formed from well-rounded greywacke boulders.
In the area of the Bay of Islands Sand Facies, the coastline is adjacent to a steep narrow coastal shelf covered with mostly locally derived sediment (i.e. the Continental Shelf). Because of the narrow, steep sea floor, there is little sediment driven onshore from the seabed. This means that the shore is sensitive to the removal of sediment (Applied Geological Associates, 1982).
In an inventory of important geological sites and landforms in the Northland region compiled by Kenny and Hayward (1993), several sites in this study area have been identified as being of geological significance. Two of these are on Motukokako (Piercy) Island, at the tip of Cape Brett. The northern half of Motukokako Island presents a well exposed example of a scarn containing babingtonite and ilvaite. Large crystals (3-5 mm) of babingtonite occur in a Pb-Zn scarn in Tertiary limestone with associated ilvaite, garnet, hedenburgite, epidote and axinite. This represents New Zealand's best ilvaite exposure, with the best of three babingtonite occurrences. This is classified as a site of international geological importance. It is also classified as a highly vulnerable site, with the major hazard being identified as the over-collecting of minerals. Motukokako Island also contains a very good example of a sea arch (the “Hole in the Rock”), classified by Kenny and Hayward (1993) as being of regional significance as “an extremely well-defined landform of scientific/educational and scenic value ”.
Flora & Fauna
The coastline from Cape Brett to Taiharuru Head provides a variety of habitats for marine and coastal flora and fauna, from open sand and gravel beaches, and open rocky shores, through to more sheltered harbour and estuarine environments.
Most of the beaches on the open coast are exposed to wave action from the ocean. They are thus highly mobile, with sediments of a size that result in high porosity. The high porosity and wave action result in penetration of well-oxygenated water deep into the sediments – layers of black, anaerobic sediments are not found close to the surface in this environment. The marine ecology of such areas is characterised by species that are comparatively mobile themselves; a necessary attribute to avoid being buried under the sand as it is moved by wave action. Crustacea are the most common type of organisms found in the inter-tidal beach area. These include the sand hoppers and sea slaters ( Talorchestia quoyana and Scyphax ornatus ) in the upper shore, species of isopods in the middle shore, and fast-burrowing amphipods and shrimps on the lower shore. Burrowing worms (polychaetes) are also common. (Morton & Miller, 1973; Dart et al., 1982). While being more visible, bivalve shellfish are generally less plentiful than the crustacea or burrowing worms. The most common bivalve are tuatua ( Paphies subtriangulata ), which occur low in the inter-tidal area.
Sand extends well offshore from most of the sandy beaches and from the larger gravel beaches. There is generally far more animal life in permanently submerged sandy areas than on the sandy shores, partly as a result of the greater stability and lack of violent wave action in sub-tidal areas. Coarser sand frequently supports dense beds of the morning star shell (“zig-zag” cockle) Tawera spissa , a bivalve shellfish about 20 or 25 mm in length. These shellfish may reach densities exceeding 5,000 per square metre in places (Dart et al., 1982). Finer sand is often occupied by large numbers of turret shell Zeacolpus pagodus , a tall-spired gastropod shellfish of 20 to 30 mm in length, which also reaches densities of several thousand per square metre. The dead shells of turret shell provide homes for hermit crabs, which can be extremely dense in patches.
Gravel sub-tidal zones tend to occur in areas close to current channels or lining the bottom of reef-top guts and surge channels, since finer sediment does not settle out of the water column when water movement is significant. Fewer organisms are found in the more mobile gravel bottom areas, but where bottom materials tend to be more stable, populations of sturdy bivalve shellfish are found. These include Tawera spissa, Gari stangeri and Glycymeris laticostata . These bivalve shellfish of gravel and sand areas are an important food resource for bottom feeding fish such as snapper and rays.
The rocky shores provided by the cliffs and inter-tidal reefs of this coastline provide habitats for a great variety of marine organisms. The types of organisms, and their distributions, are controlled mainly by level on the shore with respect to the tide, and the degree of exposure to wave action. Consequently patterns of distribution vary widely because of the complex shape of the coastline and the presence of offshore islands and reefs which can result in rapid habitat changes over short distances.
Communities of animals and plants living on open rock shores are found in a series of defined horizontal bands (“zones”) depending on their ability to cope with exposure to the drying effects of the wind and sun, and the exposure to wave action. Different types of organisms are found in each zone. This pattern of zonation is characterised by an uppermost zone of lichens and periwinkles. Below this, in areas exposed to heavy wave action, the dominant species in the middle zone are surf barnacles, Chamaesipho brunnea, and, slightly lower, Epopella plicata , accompanied by the barnacle drill Lepsiella scobina. The acorn barnacle ( Chamaesipho columna ) and native rock oysters ( Saccostrea glomerata ) replace surf barnacles in this zone in more sheltered areas. The gastropods Nerita melanotragus and Melarapha oliveri , and the limpet Notoacmea pileopsis extend from the upper zone, down through the barnacle zone, and limpets Cellana ornata and Cellana radians are found amongst the barnacles. This general pattern of species distribution may be modified in places by rock pools, shade from overhanging trees, freshwater from stream outlets, and sand scour adjacent to beaches. Where loose but fairly immobile rocks occur on the shore or in pools, a greater range of available niches leads to a further increase in the variety of marine life.
A zone of brown seaweed occurs at the bottom of the inter-tidal zone, and extends into the sub-tidal zone. The predominant seaweed species in the shallowest areas are Carpophyllum angustifolium (in areas subject to significant wave action), and Carpophyllum maschalocarpum in the more sheltered areas. In very sheltered areas, these species are replaced by the pink coloured turf-like seaweed, Corallina officinalis , and Hormosira banksii (“Neptune's necklace”).
In rocky areas below the inter-tidal zone, seaweed continues to predominate. Along with the Carpophyllum species mentioned above, Sargassum sinclairii, Carpophyllum plumosum and Landsbergia quercifolia are found at depths of 4-7 metres. The laminarian seaweed Ecklonia radiata typically has a bimodal distribution on the north-eastern coast of Northland, being found at about 5 metres below the low tide mark, and also in deeper water at 10-20 metres (Schiel, 1990). In areas of maximum wave exposure, this is replaced by Lessonia variegata in the shallower zone. Herbivorous gastropods (marine snails) (such as Cooks turban, Cookia sulcata ) and kina ( Evechinus chloroticus ) are abundant in shallow water. Less common is the spectacular purple-spined urchin Centrostephanus rodgersii, which may be found under slight overhangs or on vertical surfaces. Many of the reef fishes are most common in this habitat, as well as some of the seasonally abundant pelagic species such as blue maomao. Herbivorous fish, such as the butterfish, are found in the very shallow water, particularly in dense beds of Carpophyllum angustifolium . Individual large snapper are also occasionally seen in this habitat, particularly in summer.
Kina and Cook's turban are also found in a deeper zone featuring few large seaweeds, at a depth of about 8 metres. Kina are often present at a density of 5 to 10 per square metre in this zone, but may be more abundant than this in some localised patches (Dart et al., 1982). At this depth, (which lies between the two zones of Ecklonia ) rock flats appear comparatively bare and barren, but are however, covered in a thin layer of encrusting red algae. As observed at Mimiwhangata, the salmon pink coloured colonial ascidian (sea squirt) Didemnum candidum also sometimes colonises this habitat, covering up to 40% of the rock surface (Dart et al., 1982). Some parts of the rock flats zone may have a very sparse covering of upright clumps of the brown seaweed Carpophyllum angustifolium , which normally occur only in the most wave-exposed parts of the shallow mixed seaweed zone above this level. It is thought that kina and grazing gastropods, such as chitons, limpets and Cooks turban, play some role in keeping this zone clear of brown seaweeds (Schiel, 1990). These organisms also provide an important source of food for many reef fish.
Kina are less common in the Ecklonia forest that occurs below the rock flats, at about 10-20 metres in depth, although they may feed on the fringes of the forest. The canopy of the Ecklonia forest greatly reduces the light intensity on the rock surface beneath, providing favourable conditions for small encrusting organisms such as bryozoans, hydroids, sponges and ascidians. In the most sheltered rocky bottom areas, Carpophyllum flexuosum replaces Ecklonia at this depth. This forms a thick, tangled forest, with some individual plants reaching up to 4 metres tall. The seaweed and the rock below it are usually covered with a thin layer of detritus settled out from the relatively calm water. This detritus provides food for a range of specialised detritus and deposit feeders, such as the sea cucumber, Stichopus mollis , found on the rocks and in crevices beneath the weed canopy.
In the deep zone (25-32 metres) that occurs below the Ecklonia/Carpophyllum flexuosum forest, the flora and fauna are different. Because less light penetrates to these depths, the growth of seaweed is limited. Only scattered plants of Ecklonia occur at this depth. However, freed from competition for living space with seaweeds, sponges increase in number with increasing depth. In this zone the most important species are the massive grey Ancorina alata , the yellow or orange Polymastia granulosa , the orange branching Raspailia sp., and the tall finger-sponge Callyspongia ramosa . A few of the smaller encrusting bryozoans and sponges that were found under ledges in shallower water begin to appear on open rock structures in this zone.
In depths in excess of about 32 metres, there is insufficient light for the larger seaweed such as Ecklonia radiata to become established. At this depth the water is usually clear with a gentle fairly steady current. These conditions are ideal for a rich growth of filter-feeding animals of varieties accustomed to dim light, quiet water and low suspended sediment loading. Organisms here have delicate and diverse branching structures, much needed in quiet water to increase the filtering surface and food-gathering abilities. Tall branching sponges, such as Iophon, Raspailia, Desmacidon and Callyspongia dominate, together with hundreds of the fan shaped gorgonian Primnoides , which carpets the rock surfaces. Shaded sides of upstanding rocks may support colonies of the rare ivory coral Oculina virgosa. Small encrusting animals include bryozoans, ascidians, encrusting sponges, hydroids, cup corals and tube worms. Small red seaweeds are also found. Three conspicuous starfish, the yellow Knightaster bakeri , the cream and brown Ophidiaster mcknighti , and the multi-coloured Asterodiscus truncatus occur.
Areas of seabed with pebbles, gravel, and often sand between fist-sized rocks occur adjacent to solid rock or boulder bottoms, often forming a buffer zone between rock and sand. This is known as a “cobble” substrate. Under normal conditions, a cobble bottom is fairly stable, but during storms some of the cobbles and pebbles may move. This semi-stability allows some types of seaweeds to grow on the more stable rocks. One of the commonest seaweed in this habitat is the red seaweed Gigartina circumcincta , which grows as reddish or greenish-red sheets less than one mm thick, attached to a cobble or pebble by a tiny holdfast, three to five mm in diameter. This weed tends to be seasonal, and the size to which it grows is determined to some extent by the length of calm between successive storms. Storms readily dislodge rocks with this weed attached, which may then be cast ashore onto nearby gravel beaches. Another species of seaweed often found in this habitat, particularly in the presence of moderate amounts of sand, is the “sea rimu”, Caulerpa hypnoides , a bright green finely branched seaweed growing up from a creeping stolon (stem). In some cobble areas, larger stable rocks are scattered within this habitat. These rocks often support one or several plants of Ecklonia radiata . The organisms found living in coarse sand and gravel amongst the cobbles are similar to those found in gravel areas without cobbles (see earlier). However, the presence of cobble-sized rocks provides additional shelter for many other marine organisms that live under stones, thus increasing the diversity of flora and fauna in this habitat.
Fish species associated with reefs along the coast may change in abundance with latitude. Ward and Roberts (1986) studied the distribution and abundance of the black angelfish and eight species of wrasse, at 10 coastal (mainland) and 8 offshore island sites along the northeastern coast of New Zealand. Wrasses are reef fish that feed mostly on bottom-dwelling invertebrates. Their study showed that the number of species decreases as one goes further south, and that there was a cut-off on the coast, both in the number of wrasse species, and in the presence of black angelfish, which occurs south of Black Angel Bay (just north of Whananaki). They postulated that these differences were related to the proximity of the East Auckland Current in the northern regions.
Whales pass the coast in their seasonal migrations. Brydes whales may be encountered all year round, and minke, sei, Pseudorca , pilot whales, humpback and southern rights whales from spring to early summer.
Estuarine ecosystems occur where rivers or streams run into the seas. Major estuarine areas include the upper reaches of the Whangaruru Harbour, Whananaki Inlet, Matapouri Bay, the upper reaches of Tutukaka Harbour, and Ngunguru, Horahora, Pataua and Taiharuru Rivers. In general, estuarine areas are more sheltered than the open coast, and this allows finer sediment to settle out of the water. The percolation of water through fine sediment is more restricted than through coarser sediments, due to smaller pore sizes. This means that finer sediments become more easily depleted of oxygen, since it is the percolation of water that brings oxygen into the sediment. This, and the more sheltered conditions and lower salinity, results in habitats suited to a different range of organisms than are present on the open coast.
Typically, mangroves and saltmarsh are found in estuarine areas. Amongst the mangroves ( Avicennia marina var. resinifera ), live a variety of organisms, including gastropods (for example, the mud snail Amphibola crenata , Zediloma subrostrata, Zeacumantus lutulentus, Melagraphia aethiops, Lunella smaragda, Cominella glandiformis, and numerous smaller species such as Potamopyrgus antipodum ), burrowing worms (such as Nicon aestuarensis ) and crustacea (such as the tunnelling crab Helice crassa ). Oysters ( Crassostrea gigas and Saccostrea glomerata ) can also be found settling on the trunks and pneumatophores (aerial roots) of mangroves in some areas. Fish species in these habitats include mullet, parore, eels, flounder, and kahawai. Estuarine areas are also attractive to coastal and wading birds.
Landward of the mangrove swamps, the flats are only inundated by the sea at spring tides. Here the vegetation consists mainly of rushes and sedges (for example, the sea rush Juncus maritimus var. australiensis , the jointed rush Leptocarpus simplex and the sedge Scirpus americanus ). Beyond this lie saltmeadows, where the margin of the land has been built up due to the continued trapping of silt, and is rarely inundated by tides. Here the flora consists of such species as glasswort ( Salicornia ), and shore pimpernels ( Samolus repens ).
Estuarine areas are highly productive ecosystems. The value of mangrove forest is widely ranging:
• they are a highly productive estuarine ecosystem of vital importance in animal food webs. It has been estimated that mangroves produce up to 10 tonnes of organic plant debris/hectare/year, and enrich the nearshore environment by a factor of at least 10 over similar coastlines lacking mangroves (Ritchie, 1976);
• they have a function in oxygenating the water and sediments of harbours;
• they provide important ecological links between marine ecosystems and terrestrial and freshwater ecosystems;
• they protect coastlines from erosion;
• they provide refuge for large numbers of bird species, including forest birds in the canopy, and waders in the tidal flats;
Much coastal fishery in New Zealand is fundamentally dependent upon mangrove forests ‑ at least 30 species of fish use mangrove wetlands at some stage of their life cycle, including commercially important species. It has been reported that of fish caught commercially, 80% are linked to food chains dependent ultimately on mangroves.
A number of significant estuarine areas are found between Cape Brett and Taiharuru Head. Two of these areas, the estuarine areas in Whangaruru Harbour and Helena Bay swamp, are considered to be of outstanding significance, based on the value of the habitat to wild-life. Several other estuarine systems have been classified as being of high value. These are the Whananaki, Matapouri, Pataua/Taiharuru, Ngunguru and Horahora estuary systems (Ogle, 1982).
Approximately 2 square kilometres (i.e. 13%) of the Whangaruru Harbour are exposed at low tide (Heath, 1976). Some mud-flats occur, with extensive mangrove and jointed rush communities, which in turn grade into manuka scrub or farmland. The upper harbour consists of low mangrove, with tall mangrove fringing the channels, and extensive areas of sea rush ( Juncus maritimus ) , and jointed rush (Leptocarpus similis) on the landward edges of the harbour. At the northern end there is a freshwater marsh dominated by the sedge Scirpus fluviatilis . There is a vast area of mangroves in Punaruku embayment, grading into Juncus and Leptocarpus, with patches of the glasswort Salicornia further landward. The creeks opposite Whangaruru are of bare sand with colonising mangrove, with maturer mangrove on the south western edges. A band of Juncus maritimus occurs along the shoreline. Overall, mangroves are increasing in the harbour (Chapman, 1978; DoC, 1991).
The habitat of outstanding value in the Whangaruru Harbour includes the upper estuarine parts of the harbour and the Punaruku Estuary. These areas provide habitats for many birds, including endangered and rare species. The presence of brown teal, an endangered species listed in the International Union for the Conservation of Nature “Red Data Book”, is of particular significance, as it is regarded as New Zealand's rarest waterfowl. There is a brown teal colony at Tutaematai Stream, also small numbers at the Punaruku estuary and Ngaiotonga Stream. Other rare or endangered species include fernbird in the manuka zones, banded rail, kiwi on the fringes, and paradise shelduck. Many other common coastal and passarine birds are also present Ogle, 1982, DoC, 1991).
Vegetation surrounding the harbour includes pohutukawa. The pohutukawa in coastal areas at Whangaruru Harbour were surveyed in 1988/89 as part of an assessment of the health of the species carried out by the Forest Institute for the Department of Conservation (Hosking et al., 1989). This survey indicated that possum damage was significantly impacting on the health of the crowns of the trees. In a recent re-survey two plots on the Whangaruru Peninsula still showed significant possum damage (Hosking, 2000).
Helena Bay is also classified by Ogle (1982) as an outstanding coastal/estuarine habitat. A tidal stream, with mangroves and saltmarshes on its lower reaches, runs into Helena Bay. Cabbage trees, kahikatea and sedge swamps, overgrown ponds, and native orchids are present in the upper reaches. Some peripheral pohutukawa forest occurs, with kowhai, puriri, kohekohe, totara, and shrub areas. This area represents one of the major mainland roosts and breeding areas for brown teal, and is the largest known roost for brown teal outside Great Barrier Island. Banded rail and bittern have also been recorded here (Ogle, 1982).
Whananaki is a tidal inlet, with mud-flats grading to mangroves, then freshwater swamps, scrub, and podocarp/hardwood forest communities. Dominant bird species include white-faced heron, plover, godwit, pied stilt, gulls, and terns. The rare NZ dotterel is known to breed in this area. Other rare or endangered species recorded include fernbird, reef heron, banded rail, and banded dotterel, as well as one of Northlands largest populations of brown teal. For this reason, it is regarded as a coastal/estuarine habitat of high value (Ogle, 1982).
Matapouri Bay contains a relatively small estuary with obvious modifications resulting from roading and urban development over a period of time (Smith, NcNaught & Co. Ltd., 1974). At low tide, 35% of the area is mud-flat, sand and water, 40% mangroves, and 25% salt-marsh grading into brackish and freshwater swamps. Small patches of coastal secondary forest are continuous with the estuary, but most immediate catchment is farmed. There is a high diversity of habitats, which appear to maintain a good variety of birds. Rare or endangered species recorded in this area include brown teal (low numbers), banded rail, Caspian tern, fernbirds, Marsh crake, bittern, common sandpiper, and variable oystercatcher. The assemblage of saltmeadow plant species in the Te Wairoa Stream just south of the bridge crossing is most complete in Northland (DoC, 1991). Species present include mangrove Avicennia marina var. resinifera, Sarcocornia quinqueflora, Disphyma australe, sea rush Juncus maritimus, makaka Plagianthus divaricatus, shore pimpernels Samolus repens, jointed rush Leptocarpus similis, “yellow buttons” Cotula coronopifolia, and Suaeda novaezelandiae. Matapouri estuary has very clear water over a sand bottom. Over 40 species of fish have been recorded in the estuary (DoC, 1991).
As part of assessing local Kaimoana resources, regular surveys of pipi ( Paphies australis ) at Matapouri Bay have been undertaken by Te Whanau O Rangiwhakaahu Mäori Committee in association with the Northland Regional Council. Results of a survey undertaken over Easter 2000 indicated a significant decrease in overall numbers of pipi (particularly juveniles) compared to the previous survey in early 1999. Further data are required to determine whether such a decrease is part of natural variability within the population, or whether it is induced by adverse environmental factors such as increasing siltation (Northland Regional Council, 2000). This work is on-going.
The ecological value of the Tutukaka estuary has been reduced by the marina (DoC, 1991). A succession of reclamation and road crossings has been undertaken, and the mud-flat north west of upper harbour has been heavily modified by siting of a boat ramp and slip-way. However, some mangrove is present in the estuary, and a resident pair of the endangered brown teal has been recorded breeding at Kowhareua (DoC, 1991).
The area of coastline encompassing Ngunguru and Horahora estuaries comprises a large and complex mosaic of wetland habitats – open sand beaches, a sandspit, tidal mud-flats and sand-flats, saltmarshes and mangroves, brackish and freshwater swamps with diverse sedge, rush, shrub, flax and cabbage tree communities. The dominant vegetation is mangrove forest. Whole area is continuous with three terrestrial forested habitats, including regenerating forest at Whareora. Part of the value of the wetland lies in the rare occurrence of unbroken zones from saline to fresh water communities, through to terrestrial communities. The absence of extensive open tidal flats reduces the opportunities for both variety and numbers of wading birds, but the high proportion of vegetated wetland, with long margins where open water meets vegetation, creates habitats for some other birds on a scale unknown elsewhere in Northland (Ogle, 1982). As mentioned earlier, it is considered a high value coastal and estuarine habitat (Ogle, 1982). The area is most notable for the presence of the rare bird species, banded rail, bittern, and fernbird (at Horahora), and also occasional NZ and banded dotterels, and kiwi. Brown teal and white heron have been reported infrequently at Horahora. Also present are variable oystercatchers, pukeko, shags (little and pied) gulls, white faced heron, ducks (mallard & grey) paradise shelduck, and upland game birds (pheasant and quail). NZ dotterels breed on Ngunguru sandspit and in Horahora estuary.
The habitat at Ngunguru is relatively unmodified, but there is increasing pressure from residential development and recreational use. The area of mangrove has been recorded as increasing (DoC, 1991). The estuary at Horahora, with its small mud-flats and large expanses of mangroves and saltmarsh, is still comparatively unmodified.
The pohutukawa in coastal areas at Ngunguru Bay were surveyed in 1988/89 as part of an assessment of the health of the species carried out by the Forest Institute for the Department of Conservation (Hosking et al. 1989). This survey indicated that possum damage was significantly impacting on the health of the crowns of the trees. In a recent re-survey, a plot in Ngunguru Bay still showed significant possum damage (Hosking, 2000).
The two estuaries formed by the outflow of the Pataua and Taiharuru Rivers are almost linked. They form a series of diverse habitats consisting of small sandy beaches, sand-flat and mud-flats, and rocky islets. The Taiharuru estuary has a narrow mouth with a chain of small islands on the seaward side. The mud flats near the river mouth are comparatively hard and pebbly, but further up the estuary they are comprised of sand and soft mud.
Mangroves are the dominant species of vegetation in both estuaries. In the Taiharuru estuary mangroves are restricted to the several small creeks that run into the river, but extensive areas of mangrove are found in the Pataua estuary. Inland of mangroves, small areas of salt-marsh grade into shrub zones, where fernbird and spotless crake are found. The estuary complex is used as a feeding and nesting area by a wide variety of coastal and wading birds. Rare or endangered species recorded in this area include the Asiatic whimbrel, Caspian tern, bittern, banded rail (seen nesting and feeding in mangrove and saltmarsh), banded dotterel and NZ dotterel (DoC, 1991).
Some modification of both estuaries has occurred by reclamation, and there is heavy recreational use of the area during summer. The estuarine habitats in this area have been classified as being of moderate value by Ogle (1982).
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Ward, C. & Roberts, L. 1986. The East Auckland Current: One explanation for the distribution patterns of the coastal and offshore island fish faunas of north-eastern New Zealand. In: The offshore islands of northern New Zealand. NZ Department of Lands & Survey Information Series No. 16, Pp. 211-219.
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