Approximately 50 animal species, including mammals birds, insects and reptiles, make use of the magnetic field of the Earth for their navigation. The magnetic field of the Earth is not strong. It varies from almost 30 to 60 millionths of one tesla. By contrasting, Magnetic Resonance Imaging (MRI) birds utilize magnetic fields from 1.5 to 3.0 tesla. Therefore, scientists are not sure how exactly birds do it. Fresh studies have found that a photochemical compass might explain how migrating birds utilize this field, together with light, to find the way.
One theory explains that photoreceptors in the retina of a bird absorbs light and begins a chemical reaction which in turn, generates a photochemical species having short life and whose life span is sensitive to the direction and magnitude of a weak magnetic field.
The notion is backed by the fact that the blue light photoreceptors have been spotted in the retinas of the migratory birds when they do magnetic orientation. Though, it has not been verified that a magnetic field that is as weak as Earth’s can create noticeable transforms within a photochemical molecule. Moreover, this photochemical molecule also does not respond to the direction of a magnetic field.
German researchers have made available new proof supporting the conception that migratory birds in reality see these magnetic fields. Postdoctoral researcher Dominik Heyers and his coworkers examined garden warblers’s brains. These birds move periodically between northern Europe and southern Africa and the researchers discovered an association between neurons present in the eyes and a part of the brain thought to be engaged in migration.
To make out how the warblers see magnetic fields, the team initially had to take the birds in a migratory atmosphere; which they performed by restricting the birds’ contact to light, Heyers states. After this they injected a dye into group N, a part of the brain that is possibly connected to migration since it is extremely active at night time -when birds are eager to migrate. Then the investigators injected another dye into the eyes of the birds. The two dyes seeped along diverse sets of neurons and combined in the thalamus, a communicate station for visual instruction deep in the brain.
The information supports a hypothesis, first suggested in the 1970s, that has been strengthened by augmenting confirmation over the last 10 to 15 years that birds gather magnetic-field information with the help of special receptors in the eyes. However, researchers don’t exactly know what this receptor is, but cryptochrome; a protein recognized to be found in circadian rhythms in some animals. Cryptochrome has been discovered in the eyes of a number of migratory birds.
Researchers were already familiar with the fact that migratory birds collect information about magnetic fields from a region of their upper beak which has the magnetite receptor that consists of iron based magnetic crystals. This receptor seems to calculate the power of the magnetic field. The field is usually strong at the poles and also the angle of the field, which also fluctuates with latitude.
Heyers proposes that the visual magnetic receptor and the magnetite receptor harmonize one another, with birds making use of the receptors present in their beaks just like GPS and utilizing visual magnetic details just like a compass to find out which way they are facing.