Natures Wonders: Sea bird migration (Introduction)

by David Turell , Friday, December 22, 2023, 15:32 (337 days ago) @ David Turell

Arctic terns travel Arctic to Antarctic:

https://www.sciencealert.com/worlds-largest-seabirds-follow-sound-across-the-ocean-to-f...

"Arctic terns travel from the Arctic to Antarctica and back as part of their annual migration. Wandering albatrosses (Diomedea exulans) fly the equivalent of ten times to the Moon and back over their lifetimes.

"There has been a lot of research into how seabirds choose their flight paths and find food. They seem to use their sight or sense of smell to assess local conditions.

"Wandering albatrosses can travel more than 10,000km in a single foraging trip, though, and we don't know much about how these birds use mid- and long-range cues from their environment to decide where to go.

"For the first time, however, my team's recent study gives an insight into how birds such as wandering albatrosses may use sound to determine what conditions are like further away.

"Previous research has shown that seabirds not only seek information about where to find food, but how to do so efficiently. We discovered that the way wandering albatrosses use their sense of sound may be crucial.

"Our study looked at how these birds respond to a very low-frequency type of sound called infrasound, which can travel for thousands of kilometres.

"While it's typically inaudible to humans, we know that some animals can hear infrasound. When waves crash together or against coastlines, they create a frequency of infrasound called microbarums. This was the type of infrasound our study looked at.

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"Infrasound is also generated when waves crash against coastlines, and we know that many coastal seabirds use the coast to select their flight paths and find their way back to their breeding colonies. So, infrasound could reveal the location of static features like coastlines, giving seabirds important information across long distances.

"Despite the potential of this cue for seabirds, our paper (published in PNAS) is the first evidence that seabirds may respond to infrasound, which is monitored globally through a network of sensors installed by the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO).

"This system was installed to detect nuclear tests, but its byproduct is huge amounts of data which scientists can use. We combined the CTBTO's records with our own GPS tracking data from 89 wandering albatrosses to compare microbarums and the birds' movements.

"This allowed us to isolate data that showed how these albatrosses appeared to make decisions about where to go next. Our findings showed they chose the direction with the loudest infrasound.

"This suggests the birds could use infrasound to find food or to minimise the energy they use on their travels. However, we are not able to say for sure why louder areas are better.

Comment: Long sea migrations must have some guidance principles. We know of using the Earth's magnetic field. Using different ranges of sound is a very interesting theory. How did this evolve is the question. Short trips becoming longer over time could teach the birds to follow sounds for food. Thus a learned instinct. The alternative is coded by design.