Bell’s Sparrows (Artemisiospiza belli)) have only recently been recognized as distinct from Sagebrush Sparrows (A. nevadensis), and the “Mojave” subspecies (A. b. canescens) shares an overlapping wintering distribution with Sagebrush Sparrow in the Mojave and Sonoran deserts of southeastern California and western Arizona. We lack understanding of the 2 species’ respective wintering habitat preferences and the degree to which they interact or segregate on their wintering grounds due to the difficulty in separating them in the field and to their previous classification as one species. We captured and sampled 74 Artemisiospiza sparrows from 5 sites across western Arizona, supporting field identifications with genetic analyses of mitochondrial DNA to confirm species and molecular sexing of sampled individuals. Bell’s Sparrows and Sagebrush Sparrows segregated into different habitat types across our study area, with only one species detected at 4 of 5 study sites. Bell’s Sparrows comprised 82 percent (n = 33) of Artemisiospiza sparrows captured at the 5th site at Robbins Butte. Broadly, Sagebrush Sparrows were found in more upland, well-drained locations that were sparsely vegetated with xerophytic scrub. Bell’s Sparrows were found in more vegetated locations with halophytic Mojave seablite (Suaeda nigra) and saltbush (Atriplex) adjacent to mesquite and tamarisk woodlands. Bell’s Sparrow sex ratios were significantly female-biased (binomial test: n = 56, observed k = 48 females, expected k = 28 females for assumed p = 0.5, Pr (k ≤ 8 or k ≥ 48) < 0.0001; 95% CI = 0.369 – 0.631 for assumed p = 0.5) at Fort Mohave and Robbins Butte, the 2 sites where Bell’s Sparrows were found. Our observed sex-ratios and well-documented year-round presence of Bell’s Sparrows on and near the breeding grounds suggest that Bell’s Sparrow males and females employ different migration strategies, a phenomenon not previously documented for this taxon.

This data set includes photographs for Bell's Sparrows and Sagebrush Sparrows at 5 sites across western Arizona, captured and photographed from February 6–16, 2014. The data set also includes habitat photographs at the 5 sites. 

Artemisiospiza sparrows were captured following a flush-netting method described in Gordon (2000). Scouting was required at each site, given that a) preceding reports of recent Artemisiospiza sightings were vague as to the precise location of potential captures, the reports occasionally dated, and b) wintering Artemisiospiza are nonterritorial (Martin and Carlson 2020a). Presence of Artemisiospiza sparrows determined where nets were placed; all vegetation types were scouted at sites with multiple vegetation assemblages (Robbins Butte, Fort Mohave, Boundary Cone), and the yellow-outlined capture areas depicted in Figures 2a – 2e correspond to where Artemisiospiza sparrows were found.

Upon locating Artemisiospiza sparrows during scouting, we aligned 4 to 6 mist nets (2 x 10 m, 32- and 36-mm mesh) from end to end in a line near sighted birds, with care taken to hide nets in natural gaps in shrub cover when possible. We spaced ourselves and typically 8 to 15 volunteers into a large C-shaped semi-circle then slowly herded sparrows toward the net line. The net line was then dismantled and placed in a new location, contingent on where uncaptured birds moved while herding them toward nets or where new groups of potential captures were found. Two to approximately 12 net placements were attempted at each site, depending on the success of preceding flushing attempts.

Photographs were processed in Adobe Lightroom. We photographed captured Artemisiospiza with a Nikon digital single-lens reflex camera and 300 mm lens. We photographed each individual’s back, tail, nape, crown, profile, front, and opened wing. Each individual's set of photographs is provided in a file bearing the individual's unique USGS numbered aluminum band. File names include processing settings (e.g., sharpness, exposure) in Adobe Lightroom.

These are easily opened .jpg files.