Arctic waders and the capital‐income continuum: Further tests using isotopic contrasts of egg components

• Published in: Journal of Avian Biology
• Main Authors: Hobson, Keith A., Jehl, Joseph R.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2010
• Subjects: Arctic; Canada; Churchill; High Latitude Breeding
• Online Access: http://dx.doi.org/10.1111/j.1600-048x.2010.04980.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1600-048X.2010.04980.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1600-048X.2010.04980.x

Birds migrating annually to high‐latitude breeding grounds may benefit from the transport of endogenous nutrient reserves that ultimately contribute to reproduction. Shorebirds represent a diverse group of Arctic breeders that typically arrive on the breeding grounds with body reserves enriched in 13 C and 15 N due to wintering and staging in marine or estuarine habitats. Such isotopic differences between endogenous macronutrient reserves and local foodwebs allow the use of stable isotopes to test for the source of nutrient allocations to eggs. We examined δ 13 C and δ 15 N values in lipid‐free yolk and albumen and δ 13 C values in yolk lipid of first clutches of ten species of sandpiper and plover breeding near Churchill, Manitoba, Canada in 2003. Most birds had egg isotope values indicating a C3 terrestrial biome, which fits primarily an income (exogenous) breeding strategy. Two exceptions were single sandpiper and plover with strong marine isotope values. Among species, strong positive relationships for each isotope between egg tissue components suggest that egg proteins and lipids tended to be derived from the same isotopic source. Correlations of egg δ 13 C values for lipids and proteins approached theoretical relationships expected for exogenous breeding strategies, based on captive studies. Significant positive correlations between clutch initiation date and δ 13 C values of egg lipids and albumen suggest some endogenous nutrient contributions to later laid eggs but the circumstances under which this may occur are unstudied. Where possible, we recommend that researchers use blood and fat biopsies from laying females as a means of anchoring endogenous and exogenous endpoints for modeling of each reproductive event. We encourage the isotopic analysis of egg albumen, yolk and yolk lipids among individuals and species and tests of correlations among these components as a means of inferring origins of nutrients to eggs.