DOI: 10.5061/dryad.6m905qfxs
title: Bayesian stable isotope mixing models effectively characterize the diet of an Arctic raptor

description: 1. Bayesian stable isotope mixing models (BSIMMs) for δ13C and δ15N can be
 a useful tool to reconstruct diets, characterize trophic relationships,
 and assess spatiotemporal variation in food webs. However, use of this
 approach typically requires a priori knowledge on the level of enrichment
 occurring between the diet and tissue of the consumer being sampled (i.e.,
 a trophic discrimination factor or TDF). 2. TDFs derived from captive
 feeding studies are highly variable, and it is challenging to select the
 appropriate TDF for diet estimation in wild populations. We introduce a
 novel method for estimating TDFs in a wild population: a proportionally
 balanced equation that uses high-precision diet estimates from nest
 cameras installed on a subset of nests in lieu of a controlled feeding
 study (TDFCAM). 3. We tested the ability of BSIMMs to characterize diet in
 a free-living population of gyrfalcon (Falco rusticolus) nestlings by
 comparing model output to high-precision nest camera diet estimates. We
 analyzed the performance of models formulated with a TDFCAM against other
 relevant TDFs and assessed model sensitivity to an informative prior. We
 applied the most parsimonious model inputs to a larger sample to analyze
 broad-scale temporal dietary trends. 4. BSIMMs fitted with a TDFCAM and
 uninformative prior had the best agreement with nest camera data,
 outperforming TDFs derived from captive feeding studies. BSIMMs produced
 with a TDFCAM produced reliable diet estimates at the nest level and
 accurately identified significant temporal shifts in gyrfalcon diet within
 and between years. 5. Our method of TDF estimation produced more accurate
 estimates of TDFs in a wild population than traditional approaches,
 consequently improving BSIMM diet estimates. We demonstrate how BSIMMs can
 complement a high-precision diet study by expanding its spatiotemporal
 scope of inference and recommend this integrative methodology as a
 powerful tool for future trophic studies. 
description: This dataset contains the following files:
 "camera_data.csv": Raw prey delivery observations from
 gyrfalcon nest cameras. "GYRF_isotopes.csv":
 Raw stable isotope values (d13C & d15N) from gyrfalcon red blood
 cells. "prey_isotopes.csv": Raw stable
 isotope values (d13C & d15N) from muscle tissue samples from
 gyrfalcon prey species. Further methodological details
 can be found in the article to which this dataset is supplement
 (JAE-2020-00518).
description: Further details on this dataset and how it was used can be found
 in the attached RMarkdown document (JAE-2020-00518.Rmd). 
 *note*: the "MixSIAR" data folder contains subsets of
 the three main files formatted for use in the "MixSIAR" R
 package. Due to the computational intensity of these mixing models, we
 included the code we used to generate said models, then import them into
 the RMarkdown document via a separate .RData file
 (JAE-2020-00518_environment.RData). *note*: Some plots
 were generated using a package we wrote: "SIAplotR". A tar.gz
 file for this package is included so figures can be recreated exactly as
 they appear in the manuscript using the RMarkdown file.