By Danielle Davis
Yet another one of our beautiful Australian native birds added to our ever growing threatened and endangered list, the Pied and the Sooty Oystercatcher are beautiful, timid coastal sea birds who may abandon their ground nests, with eggs or chicks inside, when harassed or disturbed resulting in the loss of their fragile clutch. They seldom, if ever, will allow close approach and are very shy of humans – adults & children, animals such as dogs, predators like foxes & cats and also bikes and cars.
Found most commonly in coastal Tasmania and parts of Victoria, they are now thinly scattered around our Australian seashore including NSW, except for areas of unbroken sea cliffs such as the Great Australian Bight. Preferring mudflat's, sandbanks, inter tidal flats of inlets, bays and open sandy ocean beaches, they are less common along rocky or shingle coastlines. Although rarely recorded far from the coast, the Pied Oystercatcher may occasionally be found in estuarine mudflat's and short wet pastures. Where once they numbered in the hundreds of thousands, Pied Oystercatchers have now declined throughout much of their range and the current population may be as low as 10,000. Closely related forms are found in almost every continent in the world and are all facing the same challenges and population decline.
An unmistakably, large yet delicate, black and white chicken sized wader, reaching up to 51 cm in length, both the sexes look similar, but may be separable when together, with the female having a slightly longer, more slender chisel-shaped bill, which in all adults is bright orange-red. When not in flight, the Pied Oystercatcher appears entirely black above, with stark white under parts. The back, head and breast are black, and the belly, rump and tail are white. The tail is tipped black. The wings are black with a narrow white bar on the upper wing and white under wing coverts. The eye-ring, iris and long slender chisel-shaped bill of the Pied Oystercatcher are all brilliant scarlet red and their stout legs and feet are red/coral pink. Young juvenile birds are similar in appearance to the adults, but lack the intense red-orange colour in their bill, eyes and legs and are browner instead of black. The precocial downy chicks are dusky striped buff and white with black lines on back, sides of face and wings with a white under belly. The white breast and belly distinguish the Pied (two-toned) Oystercatcher from the closely related Sooty Oystercatcher, H. fuliginosus, which has all black plumage but the same bright red/orange eyes, bill, feet & legs.
Mostly silent when feeding, but otherwise quite a noisy bird, their most often heard call is a loud, sharp, high-pitched ‘kurvee-kurvee-kurvee’, usually given in alarm, which increases in pitch and rapidity when a nest site is approached, also a whistled ‘peepapeep’ or ‘pleep-pleep’ when in flight. Pairs and trios or more give ‘piping’ displays that are much the same for all sorts of breeding behavior – courtship, aggression or territorial defence. All members involved thrust their neck forward, depress their bill, and run here and there, side by side, uttering long piping trills sometimes flying to do so.
Oystercatchers forage by sight or by probing their long chisel-shaped bills in exposed sand, mud or rocks at low tide in search of bivalve and coned mollusc's, such as oysters & mussels, which are prised apart with their specially adapted bills. Finding prey, they dig them out and open by one of two methods:- either hammering or stabbing. To hammer, the bird lays a bivalve on solid ground, strikes one valve until it breaks, then inserts the scissor-like tip of its bill to cut the mollusc's adductor muscles and extract the body. To stab, the bird inserts its bill, head on the side, into the already gapping bivalve and, cutting adductor muscles and other attachments, pulls out the body. Worms, insects, crustaceans, crabs and other shell fish and small fish are also eaten. Young Pied Oystercatchers are one of the few waders that are fed by their parents using this specialised feeding technique.
Quite sedentary and sociable when not breeding they commonly roost and rest in small groups on neutral, non-territorial sand-bars, often standing on one leg (to conserve heat & energy), heads turned and bills tucked into their back to keep warm. (by blowing hot air under their wings when they exhale). Their flight is usually low, strong and direct, with regular shallow wing-beats.
Pairs mate for life and both defend their territory of some 200 m throughout the year. Breeding takes place from August – January where copulation is synchronized by call and accompanied by much wing flapping from the male. Two – three camouflaged small grey-olive, dark brown spotted long-oval shaped eggs are laid in a shallow scrape nest in sand well above the high water mark, often amongst seaweed, shell grit or small stones on coastal or estuarine beaches, sandbars or lagoons, although occasionally they use salt marsh or grassy areas. Both sexes, although mainly the female, incubate the little eggs for 28 – 32 days. The semi-precocial chicks leave the nest within 1 -3 days of hatching but are still fed by both parents for several weeks after. The eggs and chicks are defended by elaborate injury-feigning and mocking-brooding displays, and by aerial attack. The young will also sometimes hide, or enter the sea where they can swim and dive.
Disturbance to coastal feeding, nesting and roosting areas through beach-combing, fishing, dog-walking, horse-riding and 4WD vehicles.
· Predation of eggs and chicks by foxes, dogs, cats, Australian Ravens and raptors.
· Habitat destruction as a result of residential, agricultural and tourism developments.
· Hydrological changes to estuaries and similar water bodies causing modification or removal of important areas of suitable habitat.
Priority actions are the specific, practical things that must be done to recover a threatened species, population or ecological community.
The Department of Environment and Conservation has identified 14 priority actions to help recover the Pied Oystercatcher in New South Wales.
What needs to be done to recover this species?
· Undertake fox, feral cat and dog control programs.
· Assess the appropriateness of dog and cat ownership in new subdivisions and control dog walking areas especially on beaches..
· Manage estuaries and the surrounding landscape to ensure the natural hydrological regimes are maintained.
· Install interpretive signs at major nesting sites especially where 4WD cars and bikes are allowed on beaches and dog walking areas.
· Protect and maintain known or potential habitat, including the implementation of protection zones around known habitat sites and sites of recent records.
Ref:- Readers Digest Complete Book of Aust. Birds
Byron Bird Buddies - Jan Olley