Using stable-hydrogen isotopes to reveal immigration in an Arctic-breeding songbird population.

Franz Bairlein,Erica H Dunn,David J T Hussell,D Ryan Norris,Christian C Voigt

doi:10.1186/s40462-016-0081-x

Abstract

BackgroundKnowledge of immigration and emigration rates is crucial for understanding of population dynamics, yet little is known about these vital rates, especially for arctic songbirds. We estimated immigration in an Arctic population of northern wheatears on Baffin Island, Canada, by the use of stable hydrogen isotopes in tail feathers (δ2HK). We assumed that δ2HK values of juvenile (hatch-year) feathers grown at the breeding grounds were representative of the local population, while those of breeding adults were indicative of where they grew their feathers during their post-breeding molt the previous year. The extent to which adult isotope values differ from those of juveniles provides an estimate of the minimum level of immigration into the breeding population.ResultsMean δ2HK values did not differ in juvenile birds between years. Breeding adult birds did not differ significantly in mean δ2HK values compared to juveniles but did differ in their respective standard deviations, reflecting a significantly wider range of isotopic signatures in adults than in juveniles. Thirty-eight percent of the δ2HK values in adults were greater ± 2 SD of the mean δ2HK values of juveniles, suggesting that at least 38 % of the breeding adults were of non-local origin, thus immigrants from elsewhere.ConclusionsAlthough the use of stable isotopes has limitations, the use of stable-hydrogen isotopic markers has the potential to contribute valuable information towards understanding immigration rates in bird populations. In our study, hydrogen isotope measurements of the feathers of northern wheatears indicated a high rate of immigration into the breeding population, which is consistent with low return rates of banded breeding adults as well as implying high emigration rates of local breeders.Electronic supplementary materialThe online version of this article (doi:10.1186/s40462-016-0081-x) contains supplementary material, which is available to authorized users.

Highlights

Knowledge of immigration and emigration rates is crucial for understanding of population dynamics, yet little is known about these vital rates, especially for arctic songbirds
Having a closer look and comparing within a given year only (HY δ2HK values from 2010 vs all non-HY sexes into one group (AHY) δ2HK from 2011 and HY δ2HK values from 2011 vs AHY δ2HK values from 2012), we found immigration rates of at least 40 and 28 %, respectively, suggesting that there was some annual variation in immigration rates as well
Knowledge of immigration and emigration rates is crucial for full understanding of population dynamics, yet we know little about those rates in songbirds, especially arctic birds

Summary

Introduction

Knowledge of immigration and emigration rates is crucial for understanding of population dynamics, yet little is known about these vital rates, especially for arctic songbirds. We estimated immigration in an Arctic population of northern wheatears on Baffin Island, Canada, by the use of stable hydrogen isotopes in tail feathers (δ2HK). The extent to which adult isotope values differ from those of juveniles provides an estimate of the minimum level of immigration into the breeding population. Dispersal is widely regarded as a key factor driving population dynamics and rate of gene flow [1,2,3,4,5,6]. Larger-scale marking schemes have recorded some longdistance dispersal events [3] but are still limited in their ability to record shorter distance movements, and detection rates suffer from many biases. Molecular markers have been effectively used to generate quantitative estimates of dispersal [14,15,16], this approach relies on the presence of population-specific genetic signatures

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Results

Discussion

Conclusion