Evaluating created wetlands for bird diversity and reproductive success

Abstract

Wetland creation is a common conservation practice to mitigate biodiversity loss, caused by global wetland destruction. Despite this, there is a lack of large-scale evaluations of how created wetland characteristics and landscape context relate to bird diversity and reproductive success. We inventoried 89 created wetlands (0.2–20 ha) in central Sweden to investigate which local and landscape components were associated with breeding wetland bird species richness, pair abundance and reproductive success. Wetland size was positively associated with species richness, pair abundance and chick abundance. However, several small (1 ha) wetlands taken together were similar to or exceeded individual large wetlands of similar total wetland area, in terms of species richness, pair abundance, and chicks produced. While species richness showed a clear negative relationship with the proportion of the adjacent 50 m buffer composed of forest, pair abundance was positively related to the proportion of flooded grassland area and negatively related to the proportion of emergent water vegetation. Reproductive success measures showed no clear relationships to local habitat characteristics but tended to increase with a decreasing forest at the landscape scale. Our results suggest that breeding wetland bird populations could benefit from creating wetlands with a high flooded area, continuous management to minimise both the area of emergent water vegetation and the establishment of shrubs and trees in the immediate surroundings. We also suggest a practice of creating mainly small wetlands with a few larger ones to facilitate breeding wetland bird communities at the regional scale (gamma diversity).