Bird navigation has long been a subject of fascination and mystery, as these feathered creatures have been known to outsmart scientists when it comes to their navigational methods. For many years, researchers made the incorrect assumption that all birds use the same navigational approach, but we now understand that birds actually vary in their navigation methods, with many using multiple approaches.
One question that often comes up is how migratory birds are affected when the Earth's magnetic field flips around completely or changes in intensity. However, recent research suggests that birds are far from dumb and have evolved to adapt to these changes.
It's possible that bird navigation co-evolved with changes in the magnetic field, meaning that any bird that relied too heavily on it was selected against. Additionally, bird migration may have emerged in other forms before birds, possibly from an animal that migrated by foot or flew only occasionally.
Interestingly, while bird migration is a major adaptation, not all birds that are good navigators are migratory. For example, homing pigeons are famous navigators but are not migratory. This suggests that the navigational abilities incorporated into migratory behavior are also basic day-to-day getting around abilities.
Recent research from the Universität Oldenburg in Germany adds to our understanding of bird migration. The study, published in Nature, is called "Anthropogenic electromagnetic noise disrupts magnetic compass orientation in a migratory bird."
The study found that there is a lot of electromagnetic noise created by humans, which can disrupt a bird's ability to access the Earth's magnetic field for migration. The unnatural electromagnetic energy produced by many of our modern telecommunication methods can interfere with a bird's magnetic compass.
In the study, European robins exposed to background electromagnetic noise were unable to orient themselves using their magnetic compass. However, when placed in electrically grounded, aluminum-screened huts that attenuated electromagnetic noise, their magnetic orientation capabilities returned. When the grounding was removed or when broadband electromagnetic noise was deliberately generated inside the huts, the birds again lost their magnetic orientation capabilities.
Several other studies suggest a negative relationship between EMFs from mobile phone base stations and the number of house sparrows during the breeding season. One study in Flanders, Belgium found a negative and highly significant correlation between the number of house sparrow males and the strength of electromagnetic radiation from both the 900 and 1800 MHz frequency bands. This relationship was consistent across six different study areas. Another study in Valladolid, Spain found a general decline in bird density over time in areas with high electric field strength.
In India, research has revealed alarming trends in the disappearance of sparrows from areas with high levels of electromagnetic contamination caused by mobile towers. Shockingly, this decline was even more pronounced in urban areas with a greater concentration of cellphone towers. It's not just the cities that are affected either. Even rural sites with an abundance of nesting sites, food, water, and roosting sites experienced a decline in sparrow populations when exposed to high levels of electromagnetic radiation. Even more worrying, this pollution can have a cascading effect on the health of sparrow chicks by reducing the number of insects available for them to eat. The impacts of electromagnetic pollution are many and varied, affecting productivity, fertility, immunity, and even leading to habitat loss. And as the immune system of birds becomes compromised, they become more susceptible to infectious diseases, bacteria, viruses, and parasites.
The findings from these studies are unequivocal: electromagnetic noise is having a tangible effect on the behavior of our feathered friends. What is unclear is how this interference may affect bird migration patterns in the long term. It's therefore imperative that we take steps to reduce human-generated electromagnetic noise to ensure that the natural navigational abilities of these fascinating creatures are preserved for generations to come.