Bird density and diversity in braided river beds in the Upper Waitaki: Basin, South Island, New Zealand
|Title||Bird density and diversity in braided river beds in the Upper Waitaki: Basin, South Island, New Zealand|
|Publication Type||Journal Article|
|Year of Publication||1997|
|Authors||Maloney, RF, Rebergen, AL, Nilsson, RJ, Wells, NJ|
|Type of Article||paper|
|Keywords||braided river, density, diversity, survey, Upper Waitaki basin, wetland birds|
Wetland birds on 11 rivers of the Upper Waitaki Basin, South Island, New Zealand were surveyed annually between 1991 - 1994. Diversity, minimum abundance and density of birds were compared. In total 26 species of wetland birds were recorded. Minimum estimated river bird numbers were: 3566 Black-backed Gulls (Larus dominicanus), 3302 Black-fronted Terns (Sterna albostriata), 3260 Banded Dotterels (Charadrius bicinctus), 793 Black-billed Gulls (Larus bulleri), 789 Wrybills (Anarhynchus frontalis), 788 South Island Pied Oystercatchers (Haematopus ostralegus), 421 Pied Stilts (Himantopus himantopus), 85 Black Stilts (Himantopus novaezelandiae), 51 Caspian Terns (Hydroprogne caspia), and 3680 waterfowl and cormorants. Densities of birds ranged from 0.17 birds ha-1 on the Pukaki River to 0.95 birds ha-1 on the Lower Ohau River. The Cass, Lower Ohau, Godley, Tekapo and Ahuriri Rivers had higher densities of one or more species than the Upper Ohau and/or Pukaki Rivers. Densities of Black-fronted Terns, Black Stilts, Pied Stilts and Caspian Terns were negatively correlated with altitude, and in general birds preferred river sections with low or moderate flows, and low or moderate vegetation cover. Eight of the 11 rivers surveyed had more than 1% of estimated total populations of one or more of three globally vulnerable or endangered species, and in combination rivers of the Upper Waitaki Basin support almost all known Black Stilts, 15% of all Wrybills and 32% of all Black-fronted Terns. We suggest that the Upper Waitaki Basin may now provide half of all remaining suitable braided river bird habitat in New Zealand.