Researchers at the University of Michigan, the University of Texas at Arlington, Cornell University and Colorado State University released a new study relating bird migration and space weather patterns this month. The study suggests night bird migration decreases by about 9% to 17% during periods of increased solar activity, and migrating birds put less effort into flying during these periods.
Migratory birds use a variety of methods to navigate their migration, including the position of stars and the Earth’s magnetic field. While how birds use magnetism to navigate is not confirmed by the scientific community, the phenomenon is well documented. Bursts of energy from the sun can subtly disrupt Earth’s magnetic field, interfering with birds’ ability to navigate, according to the study.
The researchers focused on birds migrating through the Great Plains — a major flyway for migrating birds — between 1995 and 2018. They used weather-radar data from the National Oceanic and Atmospheric Administration to track the quantity and location of migratory birds. They primarily focused on nocturnally migrating birds because radar data detects birds at night with more accuracy.
In an interview with The Michigan Daily, Rackham student Eric Gulson-Castillo, lead author of the study, said the radar data they collected was geographically broad and relatively free of human biases.
“(The radar data collection process is) passive, there’s a large amount of it, and it is more or less measured independently of human biases,” Gulson-Castillo said. “It doesn’t matter who was on an observation platform that day. The instruments are detecting … what’s above them in the sky, regardless of the people around them.”
The solar cycle is a roughly 11-year process during which the sun’s north and south magnetic poles switch locations. Daniel Welling, U-M assistant engineering professor and study co-author, worked at UT Arlington when they began the study and spoke with The Daily about solar weather phenomenons. He explained how solar wind from the sun’s atmosphere can disrupt Earth’s magnetic field.
“Unlike the Earth’s atmosphere, the Sun’s atmosphere is so hot that it’s literally exploding away from the sun at all times and filling up the whole solar system with electrons and protons (that are) moving away from the Sun at very high speeds,” Welling said. “This is called the solar wind, and it carries with it the Sun’s magnetic field, and it drags that through the solar system … The earth has a really strong magnetic field, and the particles coming from the Sun are charged particles, so they interact with that magnetic field.”
Welling said the impacts of solar wind are not uniform, but are most pronounced during certain solar weather events.
“When you have solar flares and also events known as coronal mass ejections, which are points where parts of the solar atmosphere becomes unstable and releases a lot of mass and energy at one time, those can smack into the Earth’s magnetic field and cause it to ring and shake,” Welling said. “That’s really the time when we’re seeing the migratory patterns being most affected.”
Welling worked with Michelle Bui, an undergraduate student at UT Arlington at the beginning of the research project, to process 23 years worth of data from magnetometers across North America. Bui told The Daily she and Welling synthesized data from these magnetometers to determine when the magnetic field varied significantly from its baseline, while also taking into account that magnetic field data varies by latitude.
“(Our job was) essentially (figuring out) what kind of fluctuations are happening in the magnetometer data — what’s going on in the magnetic field is what that means — and then trying to devise a way of defining this change in magnetic field,” Bui said. “What that means is if you have a baseline of what the magnetic field normally is, there’s going to be a change, you know, separate from that magnetic field, but that’s going to vary in latitude and longitude.”
Welling also spoke on some of the limitations to their study. He explained that some of the magnetometers did not collect data for the entire 23 years, and individual magnetometers varied in the quality of data they collected each day, sometimes not collecting any data at all. Welling said one of the biggest challenges the pair faced was figuring out how to process the data in a way that accounted for these variations in data quality and availability, while still making sure the data was relevant to the location of the birds’ shown through the radar data.
“It was a process of building an algorithm that could properly account for a dynamic data set with a lot of holes and inconsistent data, and managing that big data set,” Welling said. “(We were) taking three (or) four decades of data, doing the data quality check, making sure we had a flexible algorithm to account for a lot of things, and then going back and doing the quality assurance on that.”
Gulson-Castillo also spoke about limitations to the study. He explained how the NOAA radar data the researchers used to track birds couldn’t detect differences between species, meaning the researchers couldn’t know how the varying levels of solar activity affected different kinds of birds. Gulson-Castillo said he is interested in which characteristics of individual birds might make them more susceptible to the effects of solar weather.
“I think it would be also very interesting to figure out whether there are different characteristics of birds that made some birds more likely to respond to these events than others,” Gulson-Castillo said. “Is there a difference in navigation type — group behavior versus individual migration — (or) bird size? What are the birds that are more likely to get lost than others?”
Gulson-Castillo said he is fascinated by the idea that birds on Earth are impacted at an individual level by weather in space.
“I do think that there’s something very amazing about the concept of birds responding to space weather, just in the most abstract way, because we, as humans, cannot detect it, we can at least not directly detect it right,” Gulson-Castillo said. “We can appreciate all these byproducts of it, but it’s sort of amazing to think that birds out there in the sky are impacted by these bursts of energy from the sun and are responding to it at this sort of community level population level.”
Daily Staff Reporter Abigail VanderMolen can be reached at vabigail@umich.edu.