Baltimore Oriole – Icterus galbula is a small icterid blackbird common in eastern North America as a … [+] migratory breeding bird. Orange, yellow and black color bird. Image: Getty.
Each Spring and Fall, millions of songbirds migrate up and down the central flyways of North America using navigational cues from both celestial targets and Earth’s North-South geomagnetic field lines.
Under overcast skies, the migrators must rely on their own built-in magnetoreceptors to follow Earth’s geomagnetic compass. Thought to be located in the bird’s eyes, there’s evidence that some bird species actually sense Earth’s magnetic field lines in their vision.
But things can all go wrong when space weather and solar flares wreak havoc on these field lines.
We do see that birds are navigating less well during magnetic disturbances and there’s evidence that the magnetic compass becomes more important when stars are not available, Eric Gulson-Castillo, a PhD student in ornithology and evolutionary biology at the University of Michigan in Ann Arbor, told me by phone.
Space Weather Is Notoriously Unpredictable
A magnetic field is not completely stable; they are regularly disrupted by bursts of energy from the Sun that destabilize them and make them less reliable for navigation, Gulston-Castillo, the lead author of a paper appearing this week in Proceedings of the National Academy of Sciences, told me.
That’s why occasionally, researchers will see what are known as vagrants, birds that show up well out of their normal migratory range looking lost and disoriented.
But sometimes even manmade obstacles, such as lights, which naturally attract birds, can cause disastrous results as happened last week in Chicago. That’s when almost 1000 songbirds met their death when weather pushed the birds off course when flying over Lake Michigan and into the lighted windows of Chicago’s McCormick Place convention center.