Stable isotopes can be used to infer the overwintering locations of prebreeding marine birds in the Canadian Arctic

Abstract

Although assessments of winter carryover effects on fitness‐related breeding parameters are vital for determining the links between environmental variation and fitness, direct methods of determining overwintering distributions (e.g., electronic tracking) can be expensive, limiting the number of individuals studied. Alternatively, stable isotope analysis in specific tissues can be used as an indirect means of determining individual overwintering areas of residency. Although increasingly used to infer the overwintering distributions of terrestrial birds, stable isotopes have been used less often to infer overwintering areas of marine birds. Using Arctic‐breeding common eiders, we test the effectiveness of an integrated stable isotope approach (13‐carbon, 15‐nitrogen, and 2‐hydrogen) to infer overwintering locations. Knowing the overwinter destinations of eiders from tracking studies at our study colony at East Bay Island, Nunavut, we sampled claw and blood tissues at two known overwintering locations, Nuuk, Greenland, and Newfoundland, Canada. These two locations yielded distinct tissue‐specific isotopic profiles. We then compared the isotope profiles of tissues collected from eiders upon their arrival at our breeding colony, and used a k‐means cluster analysis approach to match arriving eiders to an overwintering group. Samples from the claws of eiders were most effective for determining overwinter origin, due to this tissue's slow growth rate relative to the 40‐day turnover rate of blood. Despite taking an integrative approach using multiple isotopes, k‐means cluster analysis was most effective when using 13‐carbon alone to assign eiders to an overwintering group. Our research demonstrates that it is possible to use stable isotope analysis to assign an overwintering location to a marine bird. There are few examples of the effective use of this technique on a marine bird at this scale; we provide a framework for applying this technique to detect changes in the migration phenology of birds' responses to rapid changes in the Arctic.

The Importance of Isotopic Turnover for Understanding Key Aspects of Animal Ecology and Nutrition

“…Differences in the isotopic signature of dietary items require differences in isotopic fractionation, which can result from physical processes (e.g., geographic 2 H gradients) [9,45,46,88], metabolic pathways (e.g., C 3 vs. C 4 plant δ 13 C) [9,12,43], trophic level (e.g., plant vs. consumer δ 15 N) [9,40,44], or biome (e.g., marine vs. terrestrial δ 13 C and δ 15 N) [9,[40][41][42]. Once diet has been established, that information can then be used to answer a wide range of ecological questions, including what resources are used by different species [13,[89][90][91], where individuals move to acquire those resources [92][93][94][95], how energy and nutrients move among trophic levels [34,35,96,97], and how communities and biomes are linked by the flow of energy and nutrients [42,[98][99][100]. The diversity and novelty of these applications contribute to the great popularity of stable isotope-based diet reconstruction methods.…”

Wintering seabirds in south-west Greenland, 2017

“…Such work has already been carried out for shared populations of king and common eiders in Greenland and Canada Mosbech, Danø et al 2006;), but the studies are now more than 15 years old and there is a need to explore if movements have changed significantly in the meantime. An additional future source of complementary information may be emerging techniques using biological markers and next-generation DNA sequencing to directly assign harvested birds to source colonies or, as in the case of Steenweg et al (2017), assign breeding birds to source wintering areas.…”

Multicentury perspective assessing the sustainability of the historical harvest of seaducks

“…In comparison, sedimentary δ 15 N values were elevated relative to eider guano across a few ponds (e.g., CD044 and CD135 values approach ∼15‰). These spatial fluctuations in sedimentary δ 15 N may also reflect a variation in eider diet obtained along migration routes, which was measured in blood isotopic composition of individual eiders sampled during the prebreeding period at East Bay, mean δ 15 N of 12.4‰, with minimum and maximum values of 10.6 and 14.3‰, respectively (13). However, these elevated sedimentary δ 15 N values may also indicate catchment volatilization of ammonia in guano (39) and possibly denitrification occurring within the ponds.…”

“…The northern common eider is a long-lived seaduck with a circumpolar distribution including Arctic Canada and Greenland (10). Between 60 and 80% of the eiders breeding in Arctic Canada are estimated to migrate to southwest Greenland to overwinter (12, 13) (Fig. 1 A ).…”