Isotopic Studies of Animal Migrations

The Problem

As climate change destabilizes environments across the country, it is vital that researchers find ways to monitor the changing habitats and behaviors of plants and animals.

One method is to use stable isotopes—forms of the same element with differing numbers of neutrons— to evaluate species diets and migration in relation to climate and land-use change. Because isotopes of carbon, nitrogen, oxygen, and hydrogen vary in water and vegetation across the landscape, researchers can use those unique signatures to learn more about where animals have been and how they’ve survived.

Using isotopic signatures, researchers seek to answer questions about animals’ abilities to tolerate urban habitats, bird migration pathways and timing, and how changes in behavior may impact other processes, such as dispersal of zoonotic diseases carried by birds.

The Project

Initially led by former ERI Research Fellow Tara Smiley, an IU research team is capturing American Robins in the Bloomington area and collecting feather and claw-tip samples. Researchers attach a band to each robin’s leg, which allows them to repeatedly note any changes to each specimen. So far, the team has banded more than 200 robins.

The team sends these samples to IU’s Stable Isotope Research Facility, which uses mass spectrometry to determine what isotopes the robins picked up in their environment. By matching these isotopes to the isotopes found in various locations across the Americas, researchers can track birds’ migration patterns. They can also note any significant changes to the birds’ environment over time.

The isotope data from robins captured in Bloomington will eventually be compared with similar data being collected in other states by researchers at Georgetown University and Oklahoma University, to assess a broad range of migration habits. Combined, the data can give researchers a better picture of birds’ migratory habits and how climate change might be altering them.

The Path Forward

While researchers plan to continue sampling robins, analysis of the initial specimens is nearly complete. The team is aiming to publish the results of this project in Spring 2023.

Improved understanding of the movement of migratory and non-migratory animals could help inform conservation policy to better protect animal species. In combination with other ERI-funded research, this project is generating data that enhances researchers’ understanding of wildlife vulnerability and resilience.

Updated Aug. 18, 2022

Data from this project will be published in a paper set for publication in Spring 2023. There are also plans to publish an online visualization of the migration patterns available to the public.

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