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Methods in Ecology and Evolution








1. Income and capital breeding represent opposing ends of a continuum of reproductive strategies. Quantifying nutrient allocation to reproduction is challenging, but recent advances in compound-specific stable isotope analysis hold promise for tracing the source of individual compounds allocated to reproduction.

2. Here, we describe a novel approach of using measured carbon (δ13C) and nitrogen (δ15N) isotope values of individual amino acids (AAs) in pectoral muscle of egg-laying females and egg yolk as a useful tool to quantify the reliance on income versus capital breeding in migrating species. We used white-fronted (Anser albifrons frontalis), lesser snow (A. caerulescens caerulescens) and black brant (Branta bernicla nigricans) geese breeding in tundra ecosystems of northern Alaska as model organisms.

3. All three species relied on mixed capital-income breeding strategies, but models based on AA isotope data estimated higher proportional contributions of endogenous resources to yolk synthesis compared to results based on bulk tissue isotope analyses.

4. Tracing income versus capital nutrient allocation in migratory species at the compound level is a major advance from the current 'elemental' perspective obtained from bulk tissue stable isotope analyses. Our framework is applicable to all taxonomic groups, as long as there is a sufficient spatial or temporal isotopic gradient between resources obtained during the breeding and non-breeding periods.


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© 2023 The Authors. Methods in Ecology and Evolution published by John Wiley & Sons Ltd on behalf of British Ecological Society.

This is an open access article under the terms of the Creative Commons Attribution 4.0 International (CC BY 4.0) License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Data Availability

Article states: "Data available via the Dryad Digital Repository (Lübcker et al., 2023)."

Original Publication Citation

Lübcker, N., Whiteman, J. P., Shipley, O. N., Hobson, K. A., & Newsome, S. D. (2023). Use of amino acid isotope analysis to investigate capital versus income breeding strategies in migratory avian species. Methods in Ecology and Evolution, 14(9), 2421-2434.


0000-0002-3348-9274 (Whiteman)


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