Now that the magnetic pole reversal is in progress, some birds are having trouble migrating and are ending up in the wrong places. They're also leaving at the wrong time, because global warming is giving them false signals. It's become important for scientists to understand how birds navigate.

Amanda Onion writes on abcnews.com that how migrating birds fly for hundreds or even thousands of miles, often at night, to end up in the same spot year after year has baffled biologists for years. Some birds orient themselves using the sun or Earth's magnetic field, while others use landmarks on the ground or even familiar smells.

Biologist Henrik Mouritsen says, "How they get their magnetic sense is the last question that was left to be understood. Now we're pretty close." To learn how birds function, Mouritsen decided to intentionally confuse them. They captured songbirds in Illinois and Iowa as they made their journeys north in the spring and exposed them to a false magnetic field at dusk, then released them. The birds took off in the wrong direction, but by the second night, they had managed to correct themselves and pointed north once more.

This suggests that the birds use the setting sun to correct their internal compasses. This should help them compensate for the shifting magnetic field.

In the United States, there are four main bird routes: the Atlantic, Mississippi, Central and Pacific flyways. For birds that have flown the same route before, there's evidence that they use landmarks below them to find their way.

Hans-Peter Lipp used Velcro to attach lightweight GPS logging devices on the backs of homing pigeons, which revealed that the birds liked to travel above highways. Sometimes they even waited to see an highway exit before making a turn. Lipp says, "It's like the way a pilot of a small airplane may prefer to follow a road or powerline coincident with the compass rather than watching only the compass in the cockpit."

Scientists are still trying to learn how birds' internal compasses work. Physicists thought migrating birds may carry a protein in their eyes that is activated by blue and green light. When activated by this light (which is available both night and day), the proteins would become sensitive to Earth's magnetic field.

Mouritsen dissected some garden warblers and located the proteins in the retinas of the birds, which had just been exposed to the blue green light and to a magnetic field. He found the proteins had been altered according to the change in the magnetic field and had sent this information to the birds' brains. The birds see Earth's magnetic field superimposed over their normal vision. Mouritsen says, "Imagine a light spot with concentric darker rings around it that moves around in the retina depending on where you look. This is what the bird sees."

Native Americans know a lot about the secrets of the sky.

Photo Credit: http://www.freeimages.co.uk/