Relationship between physical characteristics of estuaries and the size and diversity of wader populations in the North Island of New Zealand

The aim of this study was to associate the distribution of waders (Charadriiformes) with physical attributes of estuaries and map the distribution of estuaries that have the potential to support large diverse wader populations. Maximum wader abundance and the maximum number of species recorded (1983-1994) at 94 estuaries on the North Island, New Zealand were related to physical attributes of the estuaries using General Linear Modelling techniques. Parameters describing the estuary type, area, tidal influence, catchment area, catchment rainfall, intertidal area and temperature were used as independent variables. Anaiysis revealed strong positive relationships between the size and diversity of a wader population and estuary area. A negative relationship between catchment runoff and wader abundance and diversity existed in some estuaries. The model predicted that relatively small estuaries (100 to 999 ha) could support large, diverse wader populations if catchment runoff was low. A map of estuaries predicted by the model to support large diverse populations of wading birds is presented. This study highlights the value of large estuaries in New Zealand in maintaining large populations and high species diversity of migratory and nonmigratory waders.