Laser-based isotope profiling in avian tissues: a high-resolution method for ecological reconstruction

Abstract Keratinous and bony tissues preserve ecological information, yet conventional isotope methods often lack the spatial resolution to detect fine-scale dietary or habitat transitions. Here, we present a high-resolution framework using laser ablation isotope ratio mass spectrometry (LA-IRMS) to reconstruct stable carbon isotope (δ 13 C) chronologies in feathers, claws, bills, and cranial bones across three avian species. LA-IRMS measurements showed strong agreement with those from conventional elemental analyzers of identical feather sections, supporting the reliability of the method for high-resolution isotope profiling. We illustrate this with three case studies that highlight the ability of LA-IRMS to resolve δ 13 C variation in archived and experimental samples. Each study comprises a single individual and serves as a methodological demonstration rather than a population-level analysis. Using 200 and 300 µm laser spacing, this minimally destructive technique achieves sub-millimeter resolution, capturing isotopic variation from near-hourly to multi-month temporal scales. In European Greenfinch, a controlled diet-shift experiment revealed clear δ 13 C transition between the original feather and its replacement. In a specimen of Marsh Warbler, δ 13 C values along the bill contour indicated enrichment over approximately 6 months of growth, while cranial bone reflected long-term isotopic averaging and region-specific variations. Archived Osprey claw exhibited prolonged foraging in tropical C₄-dominated habitats followed by a sharp δ 13 C decline near the base. These case studies demonstrate that avian keratinous tissues function as sequential archives of individual ecological history, with bone mostly reflecting integrated long-term inputs. LA-IRMS enables non-destructive, temporally explicit isotope reconstruction from archived tissues and expands opportunities for fine-scale ecological and physiological inference.