Stand structure and breeding birds: Implications for restoring ponderosa pine forests

Abstract

Fire-adapted forests in the western United States have dramatically departed from the natural or evolutionary environment over the past century because of fire suppression, logging, grazing, and other management practices. In particular, most southwestern ponderosa pine (Pinus ponderosa) forests are characterized by dense stands of small-diameter trees that are susceptible to stand-replacing crown fires and ensuing damage to watersheds, wildlife habitat, and communities at the wildland-urban interface. Restoration treatments using mechanical thinning and prescribed fire have become the dominant management paradigm in this forest type, with landscape-scale projects being implemented over the next 20 years. Although many studies have examined wildlife responses to restoration treatments, single-species information is difficult for managers to synthesize and incorporate into management decisions made at large scales. Our goal was to investigate responses of breeding birds in ponderosa pine forests to forest stand characteristics modified by restoration treatments. We sampled birds in 23 stands for 3 years in northern Arizona, and used multi-season and multi-species occupancy models to determine relationships between avian occupancy and stand attributes affected by treatment. Increasing occupancy rates and species richness were associated with decreasing canopy cover, increasing density of mature trees, and increasing density of snags. Occupancy rates and species richness were negatively associated with quadratic mean diameter, medium-sized trees, and downed woody material. Associations of the avian community and individual species with herbaceous cover and tree clumping were less consistent. Our results support the implementation of forest restoration treatments for restoring avian community occupancy in ponderosa pine forests, and emulating the evolutionary environment is likely the best approach. We recommend reducing canopy cover via thinning, and retaining trees >45.7 cm diameter at breast height and snags. A commonly-proposed diameter cap for retaining large trees after thinning (40.6 cm dbh) seems unlikely to benefit nesting passerines, as resulting tree densities would remain too large. We recommend occupancy modeling as an efficient method for assessing wildlife-habitat relationships at large scales. Ó

Long-term phenology of two North American secondary cavity-nesters in response to changing climate conditions

“…Future projections show that tree mortality in this system due to increasing drought and warmer temperatures will continue to alter habitats (Williams et al 2010;McDowell and Allen 2015). Piñon pine and ponderosa habitats are extremely important for avian species richness and diversity (Kalies and Rosenstock 2013;Johnson et al 2017;Fair et al 2018). If the current response of bluebirds is to nest at higher elevations, there may be a time when individuals will no longer be able to move to higher elevations (Freeman et al 2018).…”

Model selection and assessment for multi‐species occupancy models

“…, Broms et al. ), point‐level species richness (Kalies and Rosenstock ), metacommunity structure (Mihaljevic et al. ), and statistics associated with the differences between species’ groupings (Zipkin et al.…”

Effects of restoration and fire on habitats and populations of western hummingbirds: A literature review

“…The study found that avian responses generally only lasted 1 or 2 years, and that many species had no response to the treatments. In a study of bird responses to thinning treatments in ponderosa pine forests in Arizona, occupancy for several songbird species and species richness was generally higher in sites with larger trees and higher snag density, and lower in sites with greater canopy cover (Kalies and Rosenstock 2013). Several studies indicate that the Broad-tailed Hummingbird responds positively to logging, thinning, or other treatments that create open habitats in the southern Rockies.…”