A tiny sandpiper that turns brick red in summer and pale grey in winter. The red-necked stint is one of the smallest waders in the world. It weighs less than a tennis ball. Breeding occurs in the high Arctic where the sun never sets during the season. Wintering grounds include Australia and New Zealand. The bird flies between these hemispheres twice a year. This migration defines its existence. In breeding plumage the neck and breast are rich rufous red. The face shares this colour. The back is mottled brown and black. The bird looks as if it has been stained with rust. Outside the breeding season the appearance shifts. It becomes pale grey above and white below with a dark shoulder patch. Two birds in one. The transformation is complete and seasonal. Identification relies on these changes. Feeding involves small insects worms and crustaceans. The bird pecks rapidly at the mud. A red-necked stint feeding is a blur of motion. It does not stop. The pace is frantic. Energy intake must match the demands of migration and maintenance. The bill probes the surface layer. Prey is taken quickly. Efficiency is paramount. The call is a soft rolling 'trrrp' often given in flight. A flock of stints rising from the mudflats calls constantly. The sound carries across the estuary. It signals movement. It signals presence. The auditory cue complements the visual spectacle of thousands of birds shifting with the tide. In New Zealand these birds are common summer visitors. Arrival occurs in October. Departure happens in March. Tens of thousands overwinter on northern harbours. Kaipara. Manukau. The Firth of Thames. They are the most abundant stint in New Zealand. Their numbers dominate the coastal counts. They are a familiar sight to those who watch the tides. Breeding takes place in Siberia and Alaska. The journey south follows the East Asian-Australasian Flyway. A critical stop occurs in the Yellow Sea. Here the birds refuel. They double their body weight before continuing south. This stopover is essential. Without it the journey cannot be completed. The reliance on this specific location creates vulnerability. The population is declining. Reclamation of tidal mudflats in the Yellow Sea has removed critical habitat. The birds arrive. The mud is gone. The food source disappears. Climate change affects Arctic breeding habitat. Sea level rise threatens winter range. The pressures are cumulative. The margin for error shrinks. Confusion with the little stint is common. The little stint is rare in New Zealand. The red-necked stint has a shorter bill and a different call. These distinctions matter for accurate counting. Misidentification skews data. Careful observation is required. This is a bird of the tides. It feeds when the water is low. It rests when the water is high. The rhythm of the coast dictates its day. It moves with the water. It waits for the exposure of the mud. And then it feeds again.