Seasonal movements and habitat use of a threatened rail among fragmented riparian tidal wetlands and impoundments: management implications

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Introduction The king rail ( Rallus elegans ) is a secretive, obligate freshwater marsh specialist whose population declines and range contraction are attributed primarily to anthropogenic habitat loss. Remaining populations are concentrated along the coastal margins of its historical range in the eastern half of the United States. We investigated seasonal variation in home range size, movements and habitat use in a resident population occupying wetlands along a tidal river in the South Carolina Lowcountry. In contrast to previous studies of king rail movements in vast coastal marsh complexes, the landscape in this region was a patchwork of managed impoundments, tidal wetlands, mudflats, flooded forest and residential properties; remnants of the historical but long since abandoned commercial rice industry. Methods We used radiotelemetry to track king rails through this fragmented landscape over two years to determine breeding and non-breeding home ranges. Results Seasonal home range sizes varied (95% kernel density: 1.2–9.1 ha), but seasonal means were not significantly different. Some were among the smallest home ranges reported for king rails, reflecting high prey densities and population concentration in impounded areas. Heavier males remained in place throughout the year, but lighter males made large home range shifts between breeding and non-breeding periods. Studies across the species range have reported similar home range shifts, though the distances moved were remarkable in this region. We relate the timing and context of shifts to breeding status. Breeding king rails selected microhabitat with a high proportion of marsh vegetation near channels of water. While they avoided woody vegetation during nesting, king rails used wooded wetlands in the non-breeding season. When impoundments were flooded for overwintering waterfowl, king rails moved to adjacent tidal marsh or flooded forest. Discussion Recent rice cultivation to provide winter forage for waterfowl overlaps the breeding season, and clearing of native vegetation rendered impoundments unsuitable for king rails for several weeks. Leaving strips of unmanipulated emergent vegetation around the perimeter provided important cover during this period. Solutions are offered for minimizing impacts to king rails breeding in rice impoundments.

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