Effects of fluctuating lake levelsand habitat enhancement on black stilts(Himantopus novaezelandiae Gould, 1841)

摘要

Two questions relating to the conservation of black stilts (Himantopus novaezelandiae) wereaddressed: First, what effects do changes in lake levels have on black stilts? Second, how canhabitat be manipulated to enhance food supplies for black stilts? Relationships between lakelevels and black stilt food supplies, foraging behaviour, habitat suitability and abundance, on 4 - 6lake deltas, were investigated. On two deltas, declining water levels exposed abundant foodsupplies and large expanses of suitable habitat, and attracted more stilts to the deltas than wereusually present. On the other deltas, availability of food either decreased or did not change, andamount of suitable habitat increased as lake levels declined. Numbers of stilts using these deltaswere not related to lake levels. A specific management question was: what effects wouldextending the operating range of Lake Pukaki, to include water between 513 and 518 metresabove sea level (m a.s.l.), have on black stilts? My results suggest that food supplies and physicalhabitat are similar above and below 518 m a.s.l., and that extending the operating range wouldhave little or no effect on black stilts.The influence of site, substratum addition (straw, stones or topsoil), time, and constructionmethod (excavation or inundation) on black stilt food supplies were investigated in three fieldexperiments. Invertebrate biomass and community composition in recently created wetlands (3months old) appeared to depend primarily on site-specific conditions such as particle sizecomposition and availability of particulate organic material, but could be influenced bysubstratum additions and construction methods. Captive black stilt chicks were able to captureand consume common prey taxa that were present on experimental substrata. Wild black stiltsforaged and nested at some of the experimental wetlands. These results suggest that wetlandenhancement has excellent potential as a management technique for black stilts.