The status and distribution of rails and other marsh birds in natural and restored wetlands in northern Indiana
This study examines the status and distribution of rail populations in northern Indiana. Because rails are secretive and difficult to study, there have been few attempts in Indiana to determine the impact of wetland loss on the populations of rails and other marsh-nesting birds. There can be little doubt, however, that the loss of Indiana wetlands during historic times has caused a dramatic decline in rail populations.Using tape-recorded calls to elicit vocalizations, the status and distribution of five species of rails were studied in a 25,900 km2 area in northern Indiana in 1993 and 1994. A total of 107 surveys were conducted at 46 natural wetlands and 42 restored wetlands. The species surveyed were Sora (Porzana carolina), Virginia Rail (Rallus limicola), King Rail (Rallus elegans), Yellow Rail (Coturnicops noveboracensis), and Black Rail (Laterallus jamaicensis). Playbacks were also used to detect American Bittern (Botaurus lentiginosus), Least Bittern (Ixobrychus exilis), Marsh Wren (Cistothorus palustris) and Sedge Wren (Cistothorus platensis). Data were also collected on all other species of marsh-nesting birds detected during this study.Rails exhibited a patchy distribution. A total of 25 Soras, 33 Virginia Rails, and 1 King Rail was detected in natural wetlands in 1993. In 1994, 75 Soras, 46 Virginia Rails, and 1 King Rail was detected in the natural wetlands. A total of 30 Soras and 9 Virginia Rails was found in the restored wetlands studied in 1993 and 1994. No Yellow or Black Rails were found. Ten Least Bitterns, 31 Marsh Wrens, and 6 Sedge Wrens were detected in natural wetlands, but these species were not observed in restored wetlands.The occurrence of rails in natural wetlands was positively correlated with wetland size, presence of shrub vegetation in the watershed, amount of emergent vegetation, proximity of other wetlands, and extent of cattail cover. Negative correlations were found for human disturbance, amount of open water, and watershed characteristics. The strongest negative correlationswere found for human disturbances in or around the wetland.In restored wetlands, a significant difference was found between the occurrence of Sora and Virginia Rails with Soras occurring more frequently than Virginia Rails. A near significant difference in rail occurrence between natural and restored wetlands was also found, with rails occurring more frequently in natural wetlands, suggesting that natural wetlands surveyed may be a more suitable habitat for rails than the restored wetlands surveyed.Restored wetlands surveyed in this study failed to attract American Bitterns, Least Bitterns, Marsh Wrens or Sedge Wrens. American Bitterns were reported in natural wetlands during this study, but they were not observed.