DOI: 10.5061/dryad.9w0vt4bmd
title: Data from: Assigning harvested waterfowl to geographic origin using feather δ2H isoscapes: What is the best analytical approach?

description: Establishing links between breeding, stopover, and wintering sites for
 migratory species is important for their effective conservation and
 management. Isotopic assignment methods used to create these connections
 rely on the use of predictable, established relationships between the
 isotopic composition of environmental hydrogen and that of the
 non-exchangeable hydrogen in animal tissues, often in the form of a
 calibration equation relating feather (δ2Hf)  values derived from
 known-origin individuals and amount-weighted long-term precipitation
 (δ2Hp) data. The efficacy of assigning waterfowl to moult origin using
 stable isotopes depends on the accuracy of these relationships and their
 statistical uncertainty. Most current calibrations for terrestrial species
 in North America are done using amount-weighted mean growing-season δ2Hp
 values, but the calibration relationship is less clear for aquatic and
 semi-aquatic species. Our objective was to critically evaluate current
 methods used to calibrate δ2Hp isoscapes to predicted δ2Hf values for
 waterfowl. Specifically, we evaluated the strength of the relationships
 between δ2Hp values from three commonly used isoscapes and
 known-origin δ2Hf values from three published and one collected as part of
 this study, also grouping these data into foraging guilds (dabbling vs
 diving ducks). 
description: Samples We collected feathers from
 known-origin waterfowl across eastern Canada and the United States (n =
 273, 2017–2021). Most feather samples were collected from flightless
 hatch-year (HY) birds (i.e., ‘locals’) during regular banding operations,
 where feathers were collected opportunistically or during targeted
 sampling. We focused collection on primary (P1; clip 0.25% of the distal
 end of the feather) and covert (secondary covert; pluck entire feather)
 feathers, but due to the opportunistic nature of sampling and the
 different ages at which banding occurred for HY birds, multiple different
 feather groups, including breast feathers (n = 17) were included. We
 sampled HY American Black Duck <em>Anas rubripes</em>, Mallard
 <em>Anas platyrhynchos</em>, Ring-necked Duck <em>Aythya
 collaris</em>, and Wood Duck <em>Aix sponsa</em>. We
 also obtained Blue-winged Teal <em>Spatula discors</em> (n =
 2) samples that were collected by (Palumbo et al. 2020). Moulting adults
 (n = 9) were included if they were not flight-capable yet, but only newly
 moulted primary feathers were sampled from these birds to be sure of the
 local signal. Outside of banding stations, we also obtained primary
 feather tissue (P1; clip 0.25% of the distal end of the feather) from HY
 Wood Ducks (n = 22) banded during a Maryland breeding study, which were
 sampled within 5 km of their original banding site as flightless young. We
 obtained flight feathers (primary [P1] and primary coverts) from the
 Species Composition Survey (Gendron and Smith 20019) when wings from HY or
 adults in incomplete moult were submitted from known origins (Green-winged
 Teal <em>Anas crecca</em> n = 5, American Black Duck n = 1,
 Ring-necked Duck = 3, Common Merganser <em>Mergus
 merganser</em> n = 1, Wood Duck n = 2). Stable
 Isotope Measurements Feather samples were processed
 for <em>δ</em><sup>2</sup>H<sub>f</sub> measurement at the Laboratory for Stable-isotope Science - Advanced Facility for Avian Research (n = 71; LSIS-AFAR; Western University, London, ON, CA) and the Cornel Isotope Laboratory (n = 204; COIL; Cornel, Ithaca, NY, USA). Feathers were first cleaned of surface oils by soaking and rinsing in a 2:1 chloroform: methanol mixture and allowed to dry under a fume hood. We sampled the distal end of the feather vane and weighed 0.350 ± 0.03 mg of feather material into silver capsules. At LSIS-AFAR crushed capsules were then placed in a Uni-Prep carousel (Eurovector, Milan, Italy) heated to 60°C, evacuated and then held under positive He pressure. Feather samples were combusted using flash pyrolysis (~1350°C) on glassy carbon in a Eurovector elemental analyzer (Eurovector, Milan, Italy) coupled with a Thermo Delta V Plus continuous-flow isotope-ratio mass spectrometer (CF-IRMS; Thermo Instruments, Bremen, Germany). At COIL, the same procedures were followed, except feather samples were combusted (&gt; 1400°C) using a Thermo Scientific Temperature Conversion Elemental Analyzer coupled via a Conflo IV (Thermo Scientific) to a Thermo Scientific Delta V CF-IRMS. Both labs used the comparative equilibration method of Wassenaar and Hobson [62] using the same two keratin standards (CBS, <em>δ</em><sup>2</sup>H = -197 ‰; KHS, <em>δ</em><sup>2</sup>H = -54.1 ‰) corrected for linear instrumental drift. All results are reported for non-exchangeable H expressed in the typical delta notation, in units of per mil (‰), and normalized on the Vienna Standard Mean Ocean Water (VSMOW) scale. Based on within-run (n = 5 CBS at LSIS-AFAR; n = 7–9 Keratin at COIL) and across-run (n = 10 at LSIS-AFAR; n = 13 at COIL) analyses of standards, measurement error was approximately ± 2.5 ‰ (LSIS-AFAR) and ± 2.2 ‰ (COIL). All <em>δ</em><sup>2</sup>H<sub>f</sub> values are reported relative to the Vienna Standard Mean Ocean Water–Standard Light Antarctic Precipitation scale. Both datasets presented here were processed using the same comparative equilibration method (Wassenaar and Hobson 2003) and are comparable without rescaling (see Magozzi et al. 2021). All published data used in our study were processed using the same comparative equilibration methods we used,  using the same standards as (Wassenaar and Hobson 2003) (i.e., CFS, CHS, BWB) or used standards that have been calibrated relative to the standards in (Wassenaar and Hobson 2003) (i.e., KHS, CBS), and therefore should be comparable without any additional transformations (Magozzi et al. 2021).  Published Datasets For repeatability, we have included the final filtered dataset including all published datasets included in the associated manuscript. This file contains all the necessary data to repeat the analyses in the manuscript other than the isoscapes, which can be freely downloaded. We obtained published known-origin <em>δ</em><sup>2</sup>H<sub>f</sub> data from the assignR known-origin dataset repository (Ma et al. 2020) and authors directly. For dabbling ducks, we obtained <em>δ</em><sup>2</sup>H<sub>f</sub> data on known-origin Mallard and Northern Pintail pre-fledged HY birds captured in western North America (Hebert and Wassenaar 2005; n = 324) and known-origin juvenile and moulting adult Mallard across Europe (van Dijk et al. 2014; n = 215). Three samples from the van Dijk dataset were excluded from analyses as they did not overlap with the MA<sub>T</sub> isoscape (IDs 2755, 2932, and 2933). For diving ducks, we obtained data on known-origin HY Lesser Scaup <em>Aythya affinis</em> in western North America (Clark et al. 2006, 2009; n = 75). See the original manuscripts for more information on their sampling and stable-isotope methods. We removed outliers on a site-specific basis, where individuals with <em>δ</em><sup>2</sup>H<sub>f</sub> values more positive than the third quartile + 1.5 x the interquartile range, for that site, were removed from the calibration, as were those with <em>δ</em><sup>2</sup>H<sub>f</sub> values more negative than the first quartile – 1.5 x the interquartile range. Lit Cited Clark RG, Hobson KA, Wassenaar LI. Geographic variation in the isotopic (<em>δ</em>D, <em>δ</em><sup>13</sup>C, <em>δ</em><sup>15</sup>N, <em>δ</em><sup>34</sup>S) composition of feathers and claws from Lesser Scaup and Northern Pintail: implications for studies of migratory connectivity. Can J Zool. 2006;84: 1395–1401. doi:10.1139/Z06-135 Clark RG, Hobson KA, Wassenaar LI. Corrigendum—Geographic variation in the isotopic (<em>δ</em>D, <em>δ</em><sup>13</sup>C, <em>δ</em><sup>15</sup>N, <em>δ</em><sup>34</sup>S) composition of feathers and claws from Lesser Scaup and Northern Pintail: implications for studies of migratory connectivity. Can J Zool. 2009;87: 553–554. doi:10.1139/Z09-059 Gendron M, Smith A. National Harvest Survey website. Canadian Wildlife Service, Environment and Climate Change Canada, Ottawa, Ontario; 2019. Available: https://wildlife-species.canada.ca/harvest-survey Hebert CE, Wassenaar LI. Feather stable isotopes in western North American waterfowl: spatial patterns, underlying factors, and management applications. Wildlife Society Bulletin. 2005;33: 92–102. doi:10.2193/0091-7648(2005)33[92:FSIIWN]2.0.CO;2 Ma C, Vander Zanden HB, Wunder MB, Bowen GJ. assignR: an R package for isotope-based geographic assignment. Methods in Ecology and Evolution. 2020;11: 996–1001. doi:10.1111/2041-210X.13426 Magozzi S, Bataille CP, Hobson KA, Wunder MB, Howa JD, Contina A, et al. Calibration chain transformation improves the comparability of organic hydrogen and oxygen stable isotope data. Methods in Ecology and Evolution. 2021;12: 732–747. doi:10.1111/2041-210X.13556 Palumbo MD, Kusack JW, Tozer DC, Meyer SW, Roy C, Hobson KA. Source areas of Blue-winged Teal harvested in Ontario and Prairie Canada based on stable isotopes: implications for sustainable management. Journal of Field Ornithology. 2020;91: 64–76. doi:10.1111/jofo.12324 van Dijk JG, Meissner W, Klaassen M. Improving provenance studies in migratory birds when using feather hydrogen stable isotopes. Journal of Avian Biology. 2014;45: 103–108. doi:10.1111/j.1600-048X.2013.00232.x Wassenaar LI, Hobson KA. Comparative equilibration and online technique for determination of non-exchangeable hydrogen of keratins for use in animal migration studies. Isot Environ Healt S. 2003;39: 211–217. doi:10.1080/1025601031000096781