Effects of prescribed burning on vegetation and Swainson's warbler space use patterns in eastern Arkansas

The Swainson's warbler Limnothlypis swainsonii) is a species of conservation concern throughout the southeastern U.S. An understanding of Swainson's warbler habitat requirements has been documented, although little is known about how prescribed burning may improve or potentially negatively impact their populations. To learn more about the ecology of this secretive species and understand the effects of management on habitat use patterns, I studied the effects of prescribed burning on a population of Swainson's warblers in the St. Francis National Forest in Arkansas. With the help of coworkers, I radio-tracked 45 Swainson's warblers and collected habitat data at 1,043 sites within warbler home ranges in 2008 and 2009.;Overall, I found home-range sizes in areas occupied by Swainson's warblers with some burning ranged from 3.69--53.04 ha and unburned home-ranges sizes ranged from 2.08--23.00 ha. Home range areas with extensive burning (x¯ = 14.42 ha, SE = 3.52), partial burning (x¯ = 6.06 ha, SE = 1.34), and unburned home-range sizes (x¯ = 8.51 ha, SE = 1.04) were comparable to sizes previously reported (x¯ = 10.08 ha, SE = 1.72) from the St. Francis National Forest, although extensively burned home-range sizes were significantly larger than partially burned and unburned home-ranges sizes.;Unburned sites had greater understory vegetation cover and structure compared to burned sites within Swainson's warbler home ranges 1--2 growing seasons after burning. Likewise, points used by Swainson's warblers in both burned and unburned areas had greater understory vegetation cover and structure compared to random points within home ranges. Overall, burning caused decreases in vegetation cover and reduced vertical structure one growing season post-fire treatment; however, vegetation generally recovered to pre-burn levels 3 growing seasons after burning.;I used pitfall traps to sample arthropods at locations used by Swainson's warblers and random locations within burned and unburned home ranges. Mean abundance of total arthropods of taxa known to be selected food resources of Swainson's warblers (26.80/pitfall sample) and total mean abundance of arthropods (27.85/pitfall sample) were significantly greater at points used by warblers in burned areas compared to random points in those areas (x¯ = 19.26 and 20.88, respectively). However, this difference was opposite for unburned areas. Also, mean dry arthropod biomass tended to be greater at points used by Swainson's warblers in burned areas compared to random points in burned areas. Habitat use in this species appears to be dependent on the availability of leaf-litter cover and abundance of arthropods within burned areas. Prescribed burning, as presently done on the St. Francis National Forest, seemed to have little if any positive management effect on Swainson's warblers or other understory-dependent birds, and frequent burning of areas occupied by Swainson's warblers may lead to further decreases in habitat suitability, decreased occupancy, or even extirpation from an area.