Patterns of bird species occurrence in relation to anthropogenic and wildfire disturbance: Management implications

Abstract

We used a chronosequence approach to investigate the relationship between existing conditions of forested land that burned at some point between 1984 and 2014 in western Montana and the abundances of various bird species based on 7533 point-counts. Twelve of 68 bird species occurred significantly more frequently in burned mixed-conifer forest than in any of 13 unburned vegetation types, and most of them reached their greatest abundance in the severely burned portions of those forests. After restricting the analysis to conifer forest types only, 33 of 68 species (49%) were significantly more abundant in burned forest at some combination of time-since-fire and fire severity than in unburned conifer forest. One species, the black-backed woodpecker (Picoides arcticus), occurred nearly exclusively in severely and recently burned mixed-conifer forests. Its restricted distribution suggests that it must have evolved in the presence of those burned-forest conditions and, therefore, that it accurately reflects historical post-fire conditions that are critical to maintain on the landscape. This disturbance-dependent species was also affected strongly and negatively by both pre-fire and post-fire tree harvesting. Two important management implications follow directly from these findings: (1) the presence of the full complement of bird species in a landscape cannot be maintained through land management that either suppresses fire or acts to reduce overall fire severity through widespread forest thinning or through the application of homogeneous, low-severity, prescribed burning across the broader landscape—only severe fire can produce the variety of post-fire conditions used by species that are nowhere more abundant than in burned forests; and (2) the presence of many species (especially those most specialized to use burned forest conditions) is incompatible with both pre-fire and post-fire timber harvesting. To maintain the ecological integrity of disturbance-dependent mixed-conifer forest systems, land managers must, therefore, use strategic landscape planning to harvest trees while still retaining both an abundance of minimally disturbed, unburned, mature-forest conditions and an abundance of severely burned forest conditions that emerge from natural fire disturbance events.