Master of Science
Geography and Environment
Long, Jed A
The Earth’s magnetic field is an orientation and navigation cue for migratory animals, especially birds. However, current experiments used to test this hypothesis are limited. In my thesis, I compare different methods for combining animal tracking data with high-resolution satellite geomagnetic data by using an open-source software called MagGeo. I use the best-performing MagGeo algorithm to investigate if white storks Ciconia ciconia use geomagnetic cues to cross the eastern Sahara. Crossing this inhospitable and featureless habitat has likely selected for unique strategies that facilitate successful bird navigation during migration. I show that MagGeo can reliably be used to annotate animal movement tracks with geomagnetic data with high global accuracy. I find that white storks may use geomagnetic cues and prevailing wind conditions to cross a landscape barrier. Collectively, my work encourages further development, testing, and application of open-source data and tools to uncover relationships between migratory animals and geomagnetic data.
Summary for Lay Audience
Electric currents in the Earth’s molten outer core generate a magnetic field that extends out into space and protects the Earth from incoming solar particles. The geomagnetic field also has regular patterns which may be helpful for migratory birds crossing featureless landscapes like deserts and oceans. Like how we use a map and compass, birds with internal maps and compasses could use geomagnetic information to make movement decisions like “Which direction should I migrate?”
I test and apply a new open-source software tool called MagGeo that connects satellite geomagnetic data with location data collected by animals wearing “GPS backpacks”. I use these fused datasets to understand how animals may be using geomagnetic information to perform long-distance migration spanning thousands of kilometers.
I first do an error analysis for MagGeo by creating and testing different versions. The goal is to ensure that the software outputs are an accurate representation of how migratory animals experience the geomagnetic field. Once I identify the best MagGeo version, I use it to annotate GPS tracks of 68 white storks Ciconia ciconia crossing the eastern Sahara. I transform MagGeo outputs into values that represent 4 different ways that these birds could be making movement decisions based on geomagnetic information.
I show that we can reliably use MagGeo to study long-distance animal migration anywhere on Earth. When I apply MagGeo to study bird migration, I find that white storks migrating over the eastern Sahara use geomagnetic cues for orientation. They could also be relying on wind patterns to make movement decisions since selecting for certain wind conditions would help these bulky birds cross this risky landscape faster.
My research adds to the growing body of work that birds use multiple strategies to migrate long distances. My work also encourages development and application of new, open-source datasets and software. These tools can help explore age old questions about how animals interact with the natural world to perform the magnificent, unbelieve feat that is long-distance migration.
Iyer, Aranya, "Using high-resolution geospatial datasets to investigate the role of geomagnetic cues during long-distance bird migration" (2022). Electronic Thesis and Dissertation Repository. 8895.
Available for download on Saturday, August 31, 2024