The April 8 total solar eclipse could scramble bird behavior

Total solar eclipse: A large bird with white body, darker wings, and short hooked beak soars in a blue sky.
View at EarthSky Community Photos. | Lisa Ann Fanning in Keyport, New Jersey, captured this osprey on March 24, 2024. Lisa wrote: “Osprey continue to arrive at the Jersey Shore, reuniting with their partners (they are partner and site faithful). I enjoyed watching this bird fighting the wind today and gliding overhead.” Thank you, Lisa! With birds in the midst of their spring migration, will the darkness of the total solar eclipse have an impact on them? That’s what some researchers want to find out.
  • It’s springtime in North America, and birds are migrating from their winter habitats in the south to more northerly regions.
  • Will the total solar eclipse on April 8, 2024, have an impact on the behavior of these migrating birds?
  • Researchers will use weather radar to track the movements of birds during totality.

The Cornell Chronicle published this original post by Pat Leonard of Cornell Lab of Ornithology on March 26, 2024. Edits by EarthSky.

How will birds react during the total solar eclipse?

On April 8, the shadow of a total solar eclipse will race across North America. At the same time, researchers from the Cornell Lab of Ornithology and partners will be hurrying to measure the impact of daytime darkness on the movements of birds, bats and insects. These flying creatures are very attuned to changes in light levels. Spring migration is underway right now and with most birds flying at night, a solar eclipse could heavily impact them.

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Cecilia Nilsson, lead author of a previous Cornell Lab study when she was a Rose Postdoctoral Fellow, said:

Light is such a fundamental and ubiquitous cue, governing so many aspects of life on Earth. But it’s pretty hard to manipulate light at large scales. Here we have this unique natural phenomenon setting up a huge ‘experiment’ for us.

The path of totality as a lab

Researchers will measure airborne activity using U.S. weather radar stations in the path of the eclipse, stretching from Mexico to Texas to Maine. Signals from weather events, such as rain, are removed from the radar images, leaving only biological data: birds, insects and bats. The team will measure movements during the height of the eclipse, when the moon is directly between Earth and the sun. This is also known as totality. They’ll measure again at sunset for comparison.

According to NASA, most locations along the path of totality will be in darkness for 3.5 to four minutes, up to 4.5 minutes in Mexico. That’s not a lot of time to collect data. The researchers are building upon findings from a similar study done during the August 2017 total eclipse.

Andrew Farnsworth, a visiting researcher at the Cornell Lab and senior author of the previous study, said:

During the 2017 eclipse, we saw a decrease in flying insects, flying birds … but we didn’t see anything like the typical pattern of movement when it gets dark at night. At sunset, there is typically a big pulse of movement showing insects, birds and bats either going to ground to settle for the night or just beginning nocturnal activity.

Total solar eclipse of 2017 vs. 2024

There are several significant differences between the two eclipses, increasing anticipation about what the upcoming event could reveal. The 2017 eclipse was a total eclipse, but the moon will be a bit closer to Earth this time, making totality last longer. The 2017 solar eclipse occurred in August at the start of fall bird migration, and its shadow followed a northwest to southeast path across North America. This time, the eclipse will travel over parts of Mexico and 13 states along a southwest to northeast path and occur during spring migration.

Farnsworth said:

The timing of this eclipse is great. There are 13 radar stations along the route this time compared to eight during the 2017 event. There will be more birds on the move, seriously motivated to get to their breeding grounds. In theory, if there’s any significant change in their behavior because of unexpected darkness and the accompanying drop in temperatures, we’re much more likely to see it during this event.


Another difference: better and faster technology. In 2018, the launch of BirdCast introduced three-day migration predictions of the location and intensity of bird migration. The Cornell Lab of Ornithology and Colorado State University generate these forecasts. BirdCast’s Migration Dashboard tool even allows users to track the number of birds migrating at night through their region, right down to the county level.

Nilsson, a researcher at Lund University in Sweden, who is part of the team studying the April 8 event, said:

By seeing how animals react to the total eclipse, we can get clues to how they perceive and use light under normal circumstances. Birds and insects might use cues from light differently, for example.

The researchers will be producing a scientific paper detailing their findings.

Bottom line: Researchers with the Cornell Lab of Ornithology will be studying the reaction of birds – which are in the midst of spring migration – during the total solar eclipse of April 8.

Via Cornell University

March 31, 2024

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