The Black-billed Gull (Chroicocephalus bulleri) is endemic to New Zealand. Its natural habitats are rivers, freshwater lakes, freshwater marshes, sandy shores, pastureland and urban areas. Black-billed Gulls are the most threatened of New Zealands gull species being threatened by habitat loss. They nest predominantly on gravel river beds or shingle coastline. About half to three quarters of the world population of Black-billed Gulls nests on the river beds of the Southland region, including the Waiau, Aparima, Oreti and Mataura.