Description wikipedia

The white-fronted tern (Sterna striata), also known as tara, sea swallow, black-billed tern, kahawai bird, southern tern, or swallow tail, was first described by Johann Friedrich Gmelin in 1789. A medium-sized tern with an all-white body including underwing and forked tail, with pale grey hues on the mantle and upper side of the wing. In breeding adults a striking black cap covers the head from forehead to nape, leaving a small white strip above the black bill. This is the most abundant tern in New Zealand. It can be observed feeding on shoaling fish along the entire coastline and many of the smaller outlying islands. Breeding occurs from October to January on rocky cliffs, offshore islands and along the coast where pairs will nest on shingle, sand, shell or rock. Flocks may contain hundreds of breeding pairs that will nest in close proximity to one another. Large numbers of juveniles and some adults migrate to the south-east coast of Australia and parts of Tasmania in the autumn, with small numbers establishing breeding colonies on Flinders and Cape Barren Islands in the Bass Strait. Due to mammalian predators introduced to New Zealand, such as ferrets and stoats, the white-fronted tern has recently been given the New Zealand national conservation status of at risk/in decline.