Short-term effects of flooding on understory habitat and presence of Swainson's warblers

Understanding factors that influence changes in habitat occupancy of wetland fauna is important, particularly for species of conservation concern. One such species, the Swainson's warbler (Limnothlypis swainsonii), breeds in bottomland hardwood forests in the southeastern U.S. Because these warblers nest in the shrub layer and forage in leaf litter, they may be negatively influenced by flood-induced changes to their habitat. In 2004, we repeated song-broadcast surveys and vegetation sampling at 42 locations that were occupied by Swainson's warblers in 2000 or 2001 at four study sites in Arkansas. Only nine of 42 previously occupied locations (21%) were determined to be occupied 3-4 years after the original surveys. Occupancy changes were associated with decreases in depth and cover of leaf litter and shrub cover, and increases in cover of bare ground and forbs. These habitat and occupancy changes were associated with flooding that occurred between sample periods at three of four study sites, although detections declined at all four sites. Future conservation efforts for this species should focus on providing relatively high elevation areas that are typically free from the effects of periodic flooding.