Do animals such as birds depend so much on the magnetic field that if the field were to disappear they would drop out of the sky dead? Birds indeed do seem to rely on the magnetic field for navigational purposes. Birds have been deemed to have a “biological compass.” How they use the magnetic field is still relatively unknown. One suggestion is that they can somehow “see” the magnetic field through their eyes. A theory suggests that they absorb the light on their retina and induce chemical reactions that enable them to see the magnetic field. Additionally, a discovery has been made on how pigeon’s brain cells are somehow turned in specific directions of the magnetic field. They can “sense” the magnetic field and follow the right path to get to where they need to go. However this theory suggests it is because of their inner ear and hippocampus, not because of their eyes. Birds are not the only ones who use the magnetic field. Mice, moles, and bats also seem to have a sense of the magnetic field. If taken away from their home and given different magnetic pulls, they can always find their way back.
Now the probability of these birds falling out of the sky if the field were ever to disappear or flip is highly unlikely. Studies on what the effect would be on birds are hard to test. NOVA scientists point out that the experiments they have tried on the birds proved very little. They put the birds under a different magnetic force. At first, the birds flew in random directions, but within a few days, they adapted to the change. This goes the same for all other animals. They will adapt to change. In the past, there is no evidence pointing to the extinctions of any animals during the switching of poles or when the field has disappeared momentarily. Even if the field disappeared, there are other forces and fields with the same amount of strength that the animals can use as a guide for their migration patterns. It may take some animals a while, but eventually they all should become accustomed to the change in the magnetic field. However, scientists do not really know in-depth what would happen if the magnetic field actually disappeared. Based on their observations, they can only guess. Although the magnetic field is getting weaker, it is unlikely to disappear over the next thousand years.
Why is this important to movies? The Core has a scene where, as a result of a weak spot in the magnetic field, birds fall out of the sky, forcefully hit statues and buildings, and automatically die. Now I know they did this for entertainment purposes, but it got a little excessive. For one, birds cannot break a window just by running into them. I recall a moment at my house where a bird ran smack into the window and actually slid down the glass until it fell to the ground. Did the window break? Of course not. The window breaking is unlikely unless some evil human decides to chuck a bird at the glass. Another thing, how birds physically fly is not because of the magnetic field. They only use the magnetic field for navigational purposes. The magnetic field disappearing would not stop the birds from flying. It would only make them confused. Thanks to this movie, some will have the misconception that when the magnetic field starts to disappear, a scene from The Birds will be one of the first signs.