A plethora of bird species prefer to migrate at night as opposed to during the day, and scientists have long wondered why this is the case. Fortunately, new research published just this month in the journal Proceedings of the National Academy of Sciences (PNAS) by a team of researchers from Southern Methodist University may help answer that question.
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From what we can gather, their research pointed them in the direction of proteins known as cryptochromes, which possesses photoactive properties. While cryptochromes are known to respond to sunlight, the latest research suggests that the birds’ cryptochromes have evolved to sense and respond to magnetic fields as well.
"Although in plants and insects, cryptochromes are known to be photoactive, which means they react to sunlight. Among vertebrates much less is known, and the majority of vertebrate cryptochromes do not appear to be photoactive," elucidated Joseph Takahashi, one of the scientists who conducted the research.
"This photosensitivity and the possibility that CRY4 is affected by the magnetic field make this specific cryptochrome a very interesting molecule."
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Upon collecting protein samples from birds, harvesting them, and then analyzing them with the help of advanced laboratory equipment, the researchers were particularly puzzled to learn that the cryptochromes in migratory birds were much more complex and sensitive to light than those typically found in plants in insects.
"Cryptochromes work by absorbing a photon of light, which causes an electron to move through a sequence of amino acids. These amino acids typically consist of a chain of 3 or 4 sites that act as a wire that electrons can flow through," explained Brian D. Zoltowski, a lead author of the paper. "But in pigeons, it was identified that this chain may be extended to contain 5 sites."
As it would seem, the cryptochromes in vertebrates have evolved new mechanisms that offer enhanced abilities to ascertain light in the surrounding environment. This would purportedly give the migratory birds all the cues necessary to facilitate successful migration, and perhaps even at night when light would be scarce.
"Birds have evolved a mechanism to enhance the efficiency. So even when there is very little light around, they have enough signal generated to migrate," Zoltowski concluded.
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The question of why birds migrate at night still remains to be fully answered, but at least we can tell how they’re able to do it. Perhaps future research will shed more light on the topic and build off of what these clever researchers have learned.