Effects of Prescribed Surface Fires On Ground- and Shrub-Nesting Neotropical Migratory Birds in a Mature Indiana Oak Forest, USA

Prescribed fires have been used as a forest vegetation management tool in the eastern United States during the past decade, but concerns have been raised about direct or indirect adverse effects on Neotropical migrant bird species that nest in forest interior habitats. Prescribed fires were set in 1993 and 1995 in a mature hardwood forest in southern Indiana, USA, to reduce shade-tolerant understory woody vegetation and thereby increase the abundance and diversity of ground layer vegetation and seedlings of tree species that require moderate light levels (e.g., Querem L. spp.). The objective of this study was to determine if prescribed fires reduced the abundance or reproductive success of ground-and shrub-nesting Neotropical migrant bird species. The burned area and an adjacent unburned area were studied during the summers of 1996 and 1997. An unlimited-radius point count method was used to determine relative abundance. Nests were monitored to determine fledging success. Vegetation structure was quantified at nest sites and at random points to assess fire effects and bird nest-site selection. Abundance of birds in this nesting guild was greater in the unburned area during both years. The greatest difference in abundance was for ovenbird (Seiurus aurocappilus Linnaeus). The probability of nest success for all bird species in this nesting guild combined, determined by the Mayfield method, was significantly lower in the burned area (0.125) than in the unburned area (0.291). Abundance of the brood parasite brown-headed cowbird (Molothrus ater Boddaert) did not differ between burned and unburned areas. However, the probability of nest success for parasitized nests (0.140) was lower than that of unparasitized nests (0.735). The mean number of host young fledged from successful nests was significantly lower in parasitized nests (1.3) than from unparasitized nests (3.0). Prescribed fires significantly reduced vegetative cover in the burned area. Nest sites in the burned area had higher vegetative cover than random points, indicating that birds may have selected nest sites that were less affected by the fire. While prescribed fires that burn in a "natural" hit-or-miss pattern may retain nesting habitat for bird species in this nesting guild, lower nest success in the burned area indicates that management for desirable vegetation and for this nesting guild may not be compatible within the same forest stand at the same time. This argues for planning at a landscape l