Effects of fluctuating lake levels and habitat enhancement on black stilts (Himantopus novaezelandiae Gould, 1841)
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Two questions relating to the conservation of black stilts (Himantopus novaezelandiae) were addressed: First, what effects do changes in lake levels have on black stilts? Second, how can habitat be manipulated to enhance food supplies for black stilts? Relationships between lake levels and black stilt food supplies, foraging behaviour, habitat suitability and abundance, on 4 - 6 lake deltas, were investigated. On two deltas, declining water levels exposed abundant food supplies and large expanses of suitable habitat, and attracted more stilts to the deltas than were usually present. On the other deltas, availability of food either decreased or did not change, and amount of suitable habitat increased as lake levels declined. Numbers of stilts using these deltas were not related to lake levels. A specific management question was: what effects would extending the operating range of Lake Pukaki, to include water between 513 and 518 metres above sea level (m a.s.l.), have on black stilts? My results suggest that food supplies and physical habitat are similar above and below 518 m a.s.l., and that extending the operating range would have little or no effect on black stilts. The influence of site, substratum addition (straw, stones or topsoil), time, and construction method (excavation or inundation) on black stilt food supplies were investigated in three field experiments. Invertebrate biomass and community composition in recently created wetlands (3 months old) appeared to depend primarily on site-specific conditions such as particle size composition and availability of particulate organic material, but could be influenced by substratum additions and construction methods. Captive black stilt chicks were able to capture and consume common prey taxa that were present on experimental substrata. Wild black stilts foraged and nested at some of the experimental wetlands. These results suggest that wetland enhancement has excellent potential as a management technique for black stilts.