Recent Bayesian stable-isotope mixing models are highly sensitive to variation in discrimination factors

Alexander L. Bond, Antony W. Diamond

Research output: Contribution to journalArticlepeer-review

361 Citations (Scopus)


Stable isotopes are now used widely in ecological studies, including diet reconstruction, where quantitative inferences about diet composition are derived from the use of mixing models. Recent Bayesian models (MixSIR, SIAR) allow users to incorporate variability in discrimination factors (Δ 13C or Δ15N), or the amount of change in either δ13C or δ15N between prey and consumer, but to date there has been no systematic assessment of the effect of variation in Δ13C or Δ15N on model outputs. We used whole blood from Common Terns (Sterna hirundo) and muscle from their common prey items (fish and euphausiids) to build a series of mixing models in SIAR (stable isotope analysis in R) using various discrimination factors from the published literature for marine birds. The estimated proportion of each diet component was affected significantly by Δ13C or Δ15N. We also use recently published stable-isotope data on the reliance of critically endangered Balearic Shearwaters (Puffinus mauretanicus) on fisheries discards to show that discrimination factor choice can have profound implications for conservation and management actions. It is therefore crucial for researchers wishing to use mixing models to have an accurate estimate of Δ13C and Δ15N, because quantitative diet estimates can help to direct future research or prioritize conservation and management actions.

Original languageEnglish
Pages (from-to)1017-1023
Number of pages7
JournalEcological Applications
Issue number4
Publication statusPublished - 1 Jun 2011


  • Assumptions
  • Conservation
  • Discrimination factor
  • Management
  • Mixing model
  • MixSIR
  • Puffinus mauretanicus
  • Sensitivity analysis
  • SIAR
  • Stable isotope
  • Sterna hirundo


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