natural history - Auckland Museum

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natural history background notes | oceans gallery Banded dotterel Tuturiwhatu Charadrius bicinctus Little blue penguin Eudyptula minor Black-billed gull Karoro Larus dominicanus Wandering albatross Toroa Diomedea exulans Pied stilt Poaka Himantopus himantopus Caspian tern Taranui Hydroprogne caspia Fairy prion Titi wainui Pachyptila turtur using razor-sharp shell valves and coats its burrow with calcium carbonate. Stone borers Rock boring molluscs (piddocks) have shell structures similar to the sharply ribbed drilling bit of an oilrig. They drill down by twisting and rocking the two shell valves against the stoney substrate, enlarging the hole as the shell grows. No food is derived from the stone, the substrate providing protection for the organism. The piddocks extend siphons up into the seawater to collect food. The date mussel uses chemicals instead of physical abrasion to sculpt its stony home. It protects itself from the acid with a thick, tough outer covering. bIrds oF tHe ocean and tHe sHorelIne Birds have adapted to take advantage of every habitat found along New Zealand’s shoreline. Mudflats are rich feeding grounds for huge numbers of birds. Cliffs, rocky ledges and stacks provide breeding sites for a wide variety of sea birds. The open ocean is a feeding ground for the larger varieties of petrels. For each of these distinct environments the birds found there have evolved specialised behaviours, physiological components and physical structures to allow them to cope with the demands of the conditions present. Wading birds Wading birds specialise in probing for food in the soft mud of estuaries and harbours. New Zealand is the destination for some of the world’s Arctic waders. Breeding in the Arctic, they undertake a spectacular journey from one end of the earth to the other, to spend the northern winter in the Southern Hemisphere e.g. bar-tailed godwit, lesser knot, turnstone, Pacific golden plover, red-necked stint, sharp-tailed sandpiper, whimbrel. Some Waders breed locally and migrate within New Zealand and feed alongside Arctic migrants e.g. South Island pied oystercatcher, pied stilt. Penguins Penguins are flightless seabirds found only in the Southern Hemisphere. Descended from flying birds, 30
natural history background notes | oceans gallery their wings are now short, stiff flippers. They fly underwater, propelled by flippers alone. Their short, densely packed feathers form a smooth, firm, water- resistant coat. Their legs are short and on land give them their distinctive waddle e.g. blue penguin (the world’s smallest penguin), Fiordland crested penguin and yellow eyed penguin. Plovers and dotterels These small waders have a rounded, plump body, short legs and a short bill and tail. The bill is adapted for picking up vertebrates from wet sand or mud. When feeding they characteristically “walk and stop”, or “run-stop-peck” e.g. tuturiwhatu pukanui (New Zealand dotterel), pohowera (banded dotterel), tuturuatu (shore plover), ngutu-parore (wrybill) and the Australian spur-winged plover. shags New Zealand has twelve breeding species of shag, about a third of the world’s shag species. They are mostly seen in sheltered coastal waters, but sometimes far inland near lakes, streams and rivers e.g. kawau (black shag), karuhiruhi (pied shag), kawaupuka (little shag), parekareka (spotted shag). They are excellent fishermen, diving into the water and seizing fish with their strong beak. gulls and terns Gulls and terns usually prefer coastal situations near shore. They are sociable, feeding in flocks and breeding in colonies. Terns are more aerial and dainty than gulls with narrower pointed wings and usually a deeply forked tail. Terns have shorter legs and smaller feet e.g. Arctic skua; black- backed gull, redbilled gull, black-billed gull, black fronted tern, fairy tern, and caspian tern. Petrels New Zealand has many petrels, a group that includes albatrosses, mollymawks, shearwaters, prions and storm petrels. Feeding at sea, their effortless gliding flight enables much of their lives to be spent far from land. Predators have now driven them to breed on inaccessible islands and headlands. Larger species build open nests, but most medium and small species nest in burrows. e.g. fluttering shearwater, black petrel, flesh-footed shearwater, mottled petrel, fairy prion, and broad-billed prion. albatrosses and mollymawks Nearly three-quarters of the world’s albatross species can be found in the New Zealand region. All have a graceful, soaring flight. Many follow boats especially fishing vessels. Large numbers of albatrosses come to grief by swallowing baited hooks. Mollymawks are small albatrosses e.g. royal albatross, wandering albatross, buller’s mollymawk, black browed mollymawk. sandy eXPosed beacHes and dunes Unprotected except by distant headlands, these beaches are formed by ocean waves and prevailing winds. An exposed sandy shore is one of the most exacting and extreme habitats, supporting a group of highly specialised plants and animals. These have to withstand drying by unchecked onshore winds, and cope with burning salt spray, high temperatures and low nutrients. Pakiri (north of Auckland) is an example of a sandy exposed beach. They are composed of sand, gravel, or a mixture of both. Gravel beaches tend to be steep and tiered; sand beaches have a gentler gradient. The highest part of the intertidal area is generally the steepest. Dunes occur above the spring tide line and out of reach of waves, formed by the action of wind. Fine sands are blown inland until they meet a dune crest, log or other obstruction — they gradually build up to form a dune line. While not as diverse as the rocky shore, open sandy beaches are rich in molluscs, especially bivalves. Shells found in the strand line usually come from animals that lived within and just beyond the wave zone. However, on-shore winds can cause pelagic ocean drifters to strand on the driftline. Larger items are carried further up the shore creating the upper strand line. Items tend to get progressively smaller all the way down to the lower strand line. 31
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