Today I attended a really interesting talk by Associate Professor Phil Battley, Zoology & Ecology Group, Massey University at the local Forest and Bird branch meeting.

Red Knots … The Secrets they Hold

Despite being the second-most numerous Arctic shorebird species to visit Aotearoa, the migrations of red knots / huahou to and from their Russian breeding grounds have been largely mysterious. …

I haven't seen Red Knots at Waikawa Beach but they are found just up the road at the Manawatū Estuary.

Forest and Bird talk on Red Knots - title slide shows the birds.
Slide shows there are two subspecies and their flight paths to the Arctic.