Effects of ice storm-created gaps on forest breeding bird communities in central Vermont

A damaging ice storm struck northern New England, NY, and adjacent Canada in January 1998, affecting nearly 7 million ha of forest lands. Although relatively rare at this scale, such natural disturbances provide a unique opportunity to study short- and long-term impacts on forest ecosystems and wildlife species. I investigated the storm's short-term effects on breeding birds in a northern hardwood forest in central Vermont. Point counts (n = 52) at six ice-damaged study sites in the Green Mountain National Forest were used to compare post-storm bird abundance with pre-storm samples collected at the same points in 1993 or 1994, and at five control sites (n = 25) that were unaffected by the storm. In general, damage to canopy trees consisted of broken limbs and main stems, with lesser amounts of uprooted trees. This resulted in perforations, or small forest gaps. Overall, species richness and diversity increased only at ice storm sites, whereas total abundance increased at controls. Three forest-interior species declined in abundance (P less than or equal to 0.046) following the storm, two canopy-foragers, (Red-eyed Vireo and Blackburnian Warbler), and a ground-forager/nester normally associated with closed-canopy woodlands (Ovenbird). Another ground-forager/nester, Dark-eyed Junco, was the only species to increase in abundance (P = 0.046) after the storm, although Winter Wren showed a marginal increase (P = 0.075). Among habitat/foraging guilds, two forest-interior groups (canopy-foragers and ground/shrub foragers) declined significantly (P < 0.034), whereas open-edge ground/shrub feeders increased marginally (P = 0.069). Results from this study are consistent with investigations of bird responses to selective forest management, particularly group selection and single-tree selection, suggesting that these management strategies may effectively emulate natural disturbance events such as ice storms. (C) 2003 Elsevier B.V. All rights reserved.