Tracking Spatiotemporal Movements of Dunlin (Calidris alpina arcticola) Migration Through Stable Isotope Analysis

This thesis describes my investigations into the migratory and breeding behaviors of Dunlin (Calidris alpina arcticola) using chemical signals contained within the tissues of these long-distance migratory shorebirds. The ratios of stable isotopes (δ13C and δ 15N) in the tissues of these birds serve as an intrinsic record of past dietary consumption. By studying the variation of these ratios over time and between tissues, I was able to make inferences about past behaviors.;Chapter I describes how I exploited the change that occurs in stable carbon isotope values in blood and muscle tissues after the spring migration to estimate individual arrival dates on the breeding grounds. Doing so requires an accurate isotope turnover rate, so I evaluated an existing experimentally-determined rate and a theoretically-derived rate against an in-situ turnover rate I calculated using a novel recapture procedure developed for this study. Comparing the arrival date estimates obtained using these three turnover rates to onsite conditions and to earliest possible arrival dates determined in a subset of the sampled birds tagged with geolocation devices allowed me to evaluate their efficacies.;Chapter II expands upon the findings of the first chapter by using the arrival date estimates based on the in-situ turnover rate to improve our understanding of Dunlin behavior on the breeding grounds. I also present the stable isotope values of feather tissues which provided additional information about the isotope niches of Dunlin at different times and places. Due to their differing molt schedules, breast feathers contain isotope values reflective of the diet in the non-breeding season while the isotope values primary feathers are reflective of the diet on the breeding grounds. The variation within and between the isotope values of these two feather types provides useful insight about the distribution and behavior of Dunlin during the winter-through-summer portion of their annual cycle.