Sedge Wren Occupancy Modeling for Species Indicator

Abstract

In recent years, Oklahoma’s wintering population of Yellow Rails (Coturnicops noveboracensis) has declined, with a dramatic population crash since 2010. Because Yellow Rails are nocturnal and secretive, it can be difficult to assess whether they occur in an area without time-consuming nocturnal research. We have noticed that damp, grassy fields that contain Yellow Rails also frequently contain Sedge Wrens (Cistothorus platensis). Therefore, we hypothesized that the Sedge Wren could be a potential indicator species for the Yellow Rail. We engaged in monthly surveys staring in October 2018 for these species at Red Slough Wildlife Management Area and Sequoyah National Wildlife Refuge. Surveys were conducted at night using the rope drag method in order to flush the nocturnal rails. Any Yellow Rails and/or Sedge Wrens spotted were then caught, banded, and released. We conducted an occupancy analysis on the resulting data using the unmarked package in R. The occupancy rate for Sedge Wrens was 0.789 ± 0.236, while the occupancy rate for Yellow Rails was 0.526 ± 0.268. There was only a weak correlation between the observation of Sedge Wrens and the observation of Yellow Rails (phi = 0.35). Sedge Wrens appear to occupy a wider range of habitats than Yellow Rails, and so we feel that the use of Sedge Wrens as indicator species for Yellow Rails would not be an effective method to identify potential Yellow Rail habitats.