King rail use of rice-field and adjacent-wetland habitats in Colorado County, Texas

The king rail is a relatively unknown marsh bird which is found in natural wetlands and rice fields of southeast Texas. The extent of the impacts of rice field management practices on movements of king rails is unknown. King rails were monitored using call counts and telemetry on, and adjacent to, the Attwater Prairie Chicken National Wildlife Refuge in Colorado County, Texas to determine habitat use. Both censused and radio-tagged rails used essentially the same habitat types. King rails tended to remain within a particular area until drying conditions caused them to move to other sites. Rails used wet-prairie and marsh habitats in winter and spring. Once these sites began to dry out, rails shifted to rice fields in early summer. Rice fields were drained prior to harvest, with rice field run-off water flowing back into the wet-prairie and marsh areas. A shift in rail density was apparent with rails moving back to the marsh and wet-prairie areas. Corridors between habitats were primarily irrigation canals or ditches. King rails used marsh and wet-prairie areas in winter and spring shifting to rice fields in early summer. Rice fields and refuge marshes had higher rail densities associated with the presence of water and moderate water coverage. From November to May, rails used habitats with grass-dominated plant communities having maximum available height and cover characteristics. During May to November, rails used marsh and rice fields having 3-10 cm in water depth, 38% to 63% water coverage, and grass coverage ranging from 16% to 85%. Calling rails used shorter grasses (30 cm) compared to radio-tagged rails that used grass habitats 60 cm-70 cm in height.