Apparently dispersive in Australia;residenton northwest islands of Torres Strait. Probably no northward movement from Australia to Papua New Guinea.
Partly migratory in New Zealand. Apparently move long distances over seas:e.g.recorded Lord Howe Island and Norfolk Island;though to have invaded New Zealand from Australia twice.In Australia and New Zealand, casulal visitor to off-shore islands.
IN Australia movements correlate wityh seasonal and annual fluctuations i rainfall & availability fo wetlands.,though probably opportunistic, moving to wetlands with most suitable conditions. Regular counts throughout Australia between 1986 & 1989 (inalnd coastal) show seasonal movements to coastal sites in late summer to autumn,and leaving from coast in late winter to early spring, when there is a concomitant increase in inland countsSeasonal patterns interrupted in wet years, when greater diversity of wetlands available.IN some areas no seasonal pattern of movements detected.:e.g. Mt.Isa,Richmaond River and Sydney area.ovements to breeding areas may also depend on availabilty of wetlands:e.g. first breeding record from Swan coastal plain in WA followed heavy mid-winter rains. First bred Camden after flooding..Movement o Victoria corresponds with main breeding season (spring) after winter rains have created any suitable wetlands.
New Zealand:Availability of wetlands & prey probably ultimate factor seasonal movements. After breeding inand most of population moves to coast, amd many then moving north.Also move depending on availability of wetlands regardless of season. After breeding ,family groups & unsuccesful breeders disperse to nearby wetlands with abundant food.Movrment to coast after breeding peaks in December-January.;by February large flocks in many coastal areas on both islands.
At Queenstown, birds leave February-March;may follow river valleys to coast. After breeding at Lake Wainono, numbers of adultsand juveniles peak in summer and decrease in Autumn.
Much northward movement occurs from South Island to North Island.,especially February-April. Occur in large numbers in winter in Auckland and Northland harbours, though some winter on South sland.
Most birds winter on coast though some winter on inland wetlands.
Pre-breeding movements to south and inland begins July;by October,flocks remaining on coast are mostly non-breedersAdults leave for breeding grounds from Waimea Inlet on South Island in spring..Birds return to Queenstown late August.