Variable and South Island Pied Oystercatchers are both present on Mauao, with the former often breeding near the start of the Mauao Base Track, and folk surveying the boardwalk can easily see them. These are most regularly all black.
South Island Pied Oystercatchers breed mainly in the South Island and can be seen with the Variable group on the Matakana Island beach on Mauao. These birds are all black and white.
Variable Oystercatcher – NZ Birds on Line
South Island Pied Oystercatcher – NZ Birds on Line