Land use intensity and trace elements in raptor pellets: Evidence from two agricultural regions in Virginia, USA

Agricultural intensification can increase environmental contamination through fertilizer and pesticide use and soil disturbance, with consequences for wildlife and food webs. Raptors are effective bioindicators because they integrate exposure across trophic levels; however, noninvasive matrices beyond feathers and feces remain underutilized for chemical analysis. Here, we evaluate American kestrel (Falco sparverius) pellets as a noninvasive tool for monitoring trace element transfer in agricultural landscapes. We compared two regions in northwestern Virginia that differ strongly in land use intensity and human population density: An intensively managed production-oriented landscape (Shenandoah Valley Raptor Study Area) and a more rural system dominated by pastureland and woodland (Highland County). Between May and July 2025, we collected 185 fresh pellets from nest boxes and quantified concentrations of toxic elements (As, Cd, Ni, Pb) and potentially toxic elements (Cr, Cu, Mn, Se, Zn) using inductively coupled plasma mass spectrometry. Generalized linear mixed models with nest box ID as a random effect revealed higher concentrations of As, Cr, Cu, and Pb in the intensively managed landscape, whereas Cd, Mn, Ni, Se, and Zn did not differ between regions. Relative to published data from eastern Poland obtained with the same protocol, Virginia pellets showed markedly higher As, Cr, and Cu, especially at the intensive site, indicating a distinct regional contamination signature. Comparisons with owl pellet studies suggested broadly overlapping ranges for several elements but consistently elevated Cu and low Ni in Virginia. Our results (a) demonstrate that kestrel pellets capture land use-related differences in contaminant pathways, (b) highlight element-specific responses to agricultural intensification, and (c) support pellets as a sensitive and readily available matrix for noninvasive biomonitoring in agroecosystems.