thumbnail

The early bird gets the shrimp: Confronting assumptions of isotopic equilibrium and homogeneity in a wild bird population

Journal of Animal Ecology

By:
, ,

Links

  • The Publications Warehouse does not have links to digital versions of this publication at this time

Abstract

1. Because stable isotope distributions in organic material vary systematically across energy gradients that exist in ecosystems, community and population structures, and in individual physiological systems, isotope values in animal tissues have helped address a broad range of questions in animal ecology. It follows that every tissue sample provides an isotopic profile that can be used to study dietary or movement histories of individual animals. Interpretations of these profiles depend on the assumption that metabolic pools are isotopically well mixed and in equilibrium with dietary resources prior to tissue synthesis, and they extend to the population level by assuming isotope profiles are identically distributed for animals using the same proximal dietary resource. As these assumptions are never fully met, studying structure in the variance of tissue isotope values from wild populations is informative. 2. We studied variation in δ13C, δ15N, δ2H and δ18O data for feathers from a population of eared grebes (Podiceps nigricollis) that migrate to Great Salt Lake each fall to moult feathers. During this time, they cannot fly and feed almost exclusively on superabundant brine shrimp (Artemia franciscana). The ecological simplicity of this situation minimized the usual spatial and trophic complexities often present in natural studies of feather isotope values. 3. Ranges and variances of isotope values for the feathers were larger than those from previously published studies that report feather isotopic variance, but they were bimodally distributed in all isotope dimensions. Isotope values for proximal dietary resources and local surface water show that some of the feathers we assumed to have been grown locally must have been grown before birds reached isotopic equilibrium with local diet or immediately prior to arrival at Great Salt Lake. 4. Our study provides novel insights about resource use strategies in eared grebes during migration. More generally, it demonstrates the utility of studying variance structures and questioning assumptions implicit in the interpretation of stable isotope data from wild animals.

Additional Publication Details

Publication type:
Article
Publication Subtype:
Journal Article
Title:
The early bird gets the shrimp: Confronting assumptions of isotopic equilibrium and homogeneity in a wild bird population
Series title:
Journal of Animal Ecology
Volume
81
Issue:
6
Year Published:
2012
Language:
English
Publisher:
Wiley
Publisher location:
Hoboken, NJ
Contributing office(s):
Fort Collins Science Center
Description:
10 p.
Larger Work Type:
Article
Larger Work Subtype:
Journal Article
Larger Work Title:
Journal of Animal Ecology
First page:
1223
Last page:
1232
Country:
United States
State:
Utah
Other Geospatial:
Great Salt Lake