Territory establishment and microhabitat selection of Bachman's sparrows in a Mississippi pine forest

Abstract

Bachman's sparrows (Peucaea aestivalis) are an obligate southern open pine forest species linked to disturbance regimes (e.g., fire, windthrow) that reduce canopy cover and promote herbaceous groundcover needed for nesting, foraging, and concealment from predators. Early successional groundstory characteristics suitable for Bachman's sparrows are ephemeral in nature, raising questions about the perceived visual cues created by vegetation structural characteristics and how these characteristics influence multi‐scale habitat selection. We quantified habitat selection for 40 breeding and post‐breeding male Bachman's sparrows within 5 separately managed open pine management sub‐units at Sam D. Hamilton Noxubee National Wildlife Refuge in east‐central Mississippi, USA, from 2020–2021. We captured and color‐banded 20 individuals each year and used weekly resight locations and resource selection function models to assess factors influencing territory establishment (i.e., second‐order selection) within our study area, and microhabitat selection (i.e., third‐order selection) within territories. Bachman's sparrow territory establishment was positively influenced by evergreen cover and fire disturbance, and negatively influenced by tree canopy cover, and distance to unpaved roads. Within territories, sparrows selected areas with a greater basal area of pine (18 m2/ha), more available perching options (>9), and an abundance of native herbaceous groundcover (>36%). They also selected recently burned areas (1–3 yr) with low visual obstruction (<40 cm), and a low percent coverage of leaf litter (<33%). A better understanding of territory establishment and microhabitat selection of the Bachman's sparrow underscores the importance of frequent fire and is helpful in guiding conservation and management efforts for this declining species.