New Zealand Journal of Ecology (1999) 23(1): 53- 60

Effect of willow removal on habitat use by five birds of braided rivers, Mackenzie Basin, New Zealand

Research Article
R. F. Maloney 1
R. J. Keedwell 1
N. J. Wells 1
A. L. Rebergen 2
R. J. Nilsson 3
  1. Department of Conservation, Private Bag, Twizel, New Zealand
  2. Department of Conservation, P.O. Box 191, Masterton, New Zealand
  3. 80 Domain Terrace, Spreydon, Christchurch, New Zealand

We evaluated willow removal as a technique for enhancing habitat for birds of braided rivers by monitoring five bird species at three sites in the Mackenzie Basin, New Zealand, from 1991 to 1994 Four species—banded dotterel (Charadrius bicinctus), pied stilt (Himantopus novaezelandiae), black- fronted tern (Sterna albostriata) and South Island pied oystercatcher (Haematopus ostralegus) used the areas of riverbed cleared of willows for nesting and foraging, at the same or greater density than other areas of riverbed already free from willows. Wrybills (Anarhynchus frontalis) were occasionally seen in cleared areas of riverbed but were not nesting there during the study. Densities of banded dotterel and wrybill were lowest at sites with the greatest densities of willows, and only three out of 327 monitored nests were located in willow habitat. Nest predation rates did not differ significantly among sites with differing levels of willow infestation, nor did they differ between areas of cleared riverbed and riverbed already free from willow. In addition to weed control, predator control may be necessary to increase bird populations. This study indicates that willow removal increases foraging and nesting habitat for some river bird populations, but further surveys are necessary to assess whether willow removal has any long-term benefits.