ENHANCEMENT OF INVERTEBRATE FOOD SUPPLIES FOR BLACK STILTS BY MANIPULATING WETLAND AND STREAM SUBSTRATA

• Main Authors: Mark D. S, Richard F. Maloney
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: New Zealand; Mackenzie Basin
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.575.8116; http://www.doc.govt.nz/documents/science-and-technical/aqua2.pdf

The black stilt is an endangered species of wetland bird that now breeds only in the Mackenzie Basin, South Canterbury, New Zealand. One major cause of its decline has been the loss of wetland habitat. Attempts in the last decade to create wetlands for black stilts have not been successful, partly because artificial ponds had packed stone and silt substrata that provided few macroinvertebrates as black stilt food. We added up to four substrata (pea straw, small stones, large stones and topsoil) to 1 m2 quadrats in streams and/or ponds at three sites in an attempt to experimentally enhance invertebrate food supplies. Biomass and densities of macroinvertebrates were quantified 10 and 16 weeks after substrate additions. Invertebrate biomass was up to 18 times greater in quadrats to which pea straw had been added than in control quadrats (no substrate added). Biomass of invertebrates in pea straw, small stone and large stone substrata all exceeded a putative nesting threshold for black stilts of 1 g m-2. Xanthocnemis zealandica, Physa acuta and Oligochaeta were particularly abundant on pea straw, whereas Deleatidium spp. and Aoteapsyche sp. were most common on stones. These experiments provide the basis for ongoing research on macroinvertebrate enhancement in wetland areas used by black stilts.