Masked Lapwings are a common bird that is often seen in towns and cities, even nesting in parks and on top of blocks of flats. They can be quite aggressive when raising young and can attack people if they get too close to the chicks. They are the largest member of the lapwing family (35-38 cm) and occur in two races - northern birds are ssp novoehollandiae, while southern and eastern birds are miles, which used to be considered a separate species known as the Spur-winged Plover on account of the spike on the wing joint. They use this spike to inflict injuries on other birds and animals. These birds can make a lot of noise day and night, which can make them unpopular in residential areas.
The first photo is an adult of race miles, while the next two are juveniles (middle is older, bottom younger) of the same race. The last photo is an adult of race novaehollandiae
1: Camperdown Campus, University of Sydney, 08/09/2009.
2: Royal Botanic Gardens, Sydney, NSW, 13/09/2009.
3: Royal Botanic Gardens, Sydney, NSW, 30/12/2010.
4: Cairns Esplanade, Qld, 13/10/2011.