Upon further research, South Island Oystercatchers nest in gravel banks in braided rivers, which explains why this one was flying...

South Island Oystercatcher

New Zealand | 2008

Upon further research, South Island Oystercatchers nest in gravel banks in braided rivers, which explains why this one was flying around me aggressively as I forded the Waimakariri River. Photo © copyright by Jack Brauer.