Reconstructing dietary strategies in past urban environments is challenging because of the complexity of anthropogenic impacts on food webs, in which diverse local and imported resources with variable isotopic compositions limit the interpretive power of conventional bulk-collagen stable isotope analysis. We address this problem using domestic cats as dietary proxies, exploiting their opportunistic foraging behavior to track resource partitioning within a medieval urban landscape. We present an integrated multi-isotope study of cat bone collagen from medieval Gdańsk (northern Poland) and six regional comparative sites, combining bulk collagen δ13C, δ15N, and δ34S analysis with compound-specific δ13C and δ15N analysis of amino acids. Despite apparent isotopic homogeneity in the Gdańsk assemblage within the conventional bulk collagen dual-isotope space, the expanded isotopic framework reveals substantial individual-level dietary variability. Sulfur isotopes indicate diverse food provenances, including baseline values of the marine ecosystem and grain imported from inland regions. Amino acid-based fingerprinting identifies diets spanning terrestrial C3 and C4, freshwater, and marine ecosystem baselines, while amino acid-based trophic position proxies reveal highly variable individual trophic levels uncorrelated with bulk collagen δ15N values. These findings demonstrate that isotopic homogeneity in the conventional dual-isotope space can mask substantial dietary heterogeneity. Our study highlights the potential of integrating amino acid analysis with sulfur isotope analysis to reconstruct individual-level food choices in complex past environments.
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RBINS Staff Publications 2026
As the offshore wind energy technology is rapidly progressing and because wind turbines at sea have a relatively short life span, repowering scenarios are already being discussed for the oldest wind farms. Ongoing developments result in larger wind turbines and an increased open airspace between turbines. Despite taller towers having larger rotor swept zones and therefore a higher collision risk area compared to smaller-sized turbines, there is increasing evidence that fewer but larger, more power-efficient turbines may have a lower collision rate per installed megawatt. As such, turbine size can offer an opportunity to mitigate seabird fatalities by increasing the clearance below the lower rotor tip. We assessed the seabird collision risk for a hypothetical repowering scenario of the first offshore wind farm zone in Belgian waters with larger turbines and the effect of an additional increase in hub height on that theoretical collision risk. For all species included in this exercise, the estimated collision risk decreased in a repowering scenario with 15 MW turbines (40.4% reduction on average) because of higher clearance between the lower tip of the turbine rotor and the sea level, and the need for a lower number of turbines per km². Increasing the hub height of those 15 MW turbines with 10 m, further decreases the expected number of seabird collisions with another 37% on average. However, terrestrial birds and bats also migrate at sea and the effect of larger turbines on these taxa is less clear. Possibly even more terrestrial birds and bats are at risk of collision compared to the current turbines. So, while larger turbines and increasing the hub height can be beneficial for seabirds, this likely needs to be applied in combination with curtailment strategies, which stop the turbines during heavy migration events, to reduce the impact on other species groups.
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RBINS Staff Publications 2022
