Habitat and Ecology
Habitat and Ecology
Behaviour Although this species is largely sedentary some southern populations migrate north after the breeding season1. The species breeds between late-September and January1, 2 in colonies of up to several hundred pairs (occasionally nesting solitarily)1 and remains gregarious outside of the breeding season2. Habitat It inhabits sheltered coastal1, 3 harbours, bays, inlets, estuaries, beaches and rocky shores3, usually foraging within 10 km of the shore but also following fishing boats beyond the continental shelf1, 3. It may forage and roost in near-coastal inland habitats including lagoons2, 3, lakes, swampy basins, rivers, streams3, reservoirs1, pastures1, 3, cultivated land, tussock grassland, scrubland and cleared areas in pine plantations3. It often also forages around abattoirs, fish- or seafood-factories and at sewage outfalls1. The species will form breeding colonies in a number of locations including headlands1, 3, sea cliffs1, 3, 2, rocky outcrops, stacks3, 2, offshore islands1, 3, 2, low sandy, pebbly or rocky beaches, spits or islands1, 3 in estuaries and lagoons2, on reefs, peninsulas, mudflats, sandbanks3 and occasionally on the roofs of coastal buildings or in salt and sewage works2. Locally (e.g. in New Zealand) it may also breed inland on flat rocky mountaintops near permanent water3. Diet Its diet consists of molluscs (e.g. mussels, cuttlefish Sepia spp. and terrestrial snails), echinoderms1, 2, sponges2, arthropods (e.g. swarming termites, crabs, isopods, amphipods)1, 2, macrozooplankton2, fish, worms, reptiles1 (e.g. snakes)2, amphibians1 (e.g. frogs)2, small mammals1, 2, birds1 and berries2. The species also scavenges refuse, sewage and carrion1, 2. Breeding site The nest is a bulky structure of dried plants or seaweed1 placed on bare rock, sand or mud substrates1, 3 in well-vegetated sites1 (with grasses, sedge, rushes and other herbaceous plants)3 at the base of bushes, trees, rocks1, walls2 or other vertical structures1. Breeding habitats include headlands1, 3, sea cliffs1, 3, 2, rocky outcrops, stacks3, 2, offshore islands1, 3, 2, reefs, peninsulas, mudflats, sandbanks3, the roofs of coastal buildings, salt and sewage works, guano platforms, shipwrecks2 and above the high water mark on low sandy, pebbly or rocky beaches1, 3, spits or islands3 in estuaries and lagoons2. Locally (e.g. in New Zealand) it may also breed inland on flat rocky mountaintops near permanent water3. Management information Attaching high-visibility plastic cones to trawler warp cables can significantly reduce the mortality and bycatch of this species due to trawler fisheries7.