Marsden, I. D., & Soper, E. (2009). Estuarine research report 40: Abundance and distribution of wetland birds and food resources in the Charlesworth Wetlands, summer 2008-9. University of Canterbury.
The Charlesworth Wetlands in Te Ihutai estuary were created in two parts in 1991 and 2001 to provide roosting, nesting, and feeding habitats for shore and wading birds. This report investigated the number and distribution of birds, food resources available for birds, and sediment trace metals and nutrients in Charlesworth marsh locations in the summer of 2008-2009.
Overall, 24 wading, shore, and passerine birds were observed utilising the Charlesworth wetlands and displaying a range of behaviours, including pied stilts, bar-tailed godwits, and white-faced herons. Bird abundance and diversity was higher in the new marsh compared to the old marsh. The Charlesworth wetland was found to be an important roosting and nesting habitat for shore and wading birds, especially at high tide. At high tide, aquatic food resources consisted of terrestrial insect larvae, polychaete worms, and small marine invertebrates. Marine invertebrates in the restored wetlands also provided additional food resources when the estuary was inundated at high tide.
Notably, the Canterbury earthquakes in 2010 and 2011 considerably disrupted marsh areas within Charlesworth wetland, flattening channel edges and increasing sediment. Benthic sediments comprised mainly fine sediment and were often anoxic several mm below the surface. Following its findings, the report recommended more rigorous, long-term research in Charlesworth and similar wetlands within Te Ihutai to determine restoration success, especially following the earthquakes.