White-bellied Sea-eagle
Haliaeetus leucogaster

The second-largest bird of prey in Australia (75-85 cm in length, 180-220 cm wingspan), these birds are an impressive sight when they soar over esturaies or bays, looking for fish, birds or carrion. The adults have black-and-white plumage (as shown here) while the juveniles are browner. They are moderately common, although at a distance, it might be possible to mistake it for a pelican.
 

1: Cairns Esplanade, Qld, 13/10/2011.
2: North Head Sanctuary, Manly, NSW, 04/07/2010.