How do birds know which direction is south?

Question

And how do they know when to fly south?

If something tells the birds that they should be flying south, then how do pet birds (I have 3) know NOT to fly south?

Answer 1

The navigate mainly by the setting sun and an internal magnetic "compass." There's still a little debate over whether other cues exist like the stars. (See source below.)

Day length seems to be the primary cue for migrating (not unlike plants).

Although, an interesting fact, pigeons in the UK have been found following highways to migrate.

Answer 2

Birds use sun and moon positions as navigation aids. If you keep the rising sun on your left you can also fly south. Some birds have a compass sense and also magnetic sense so that they can also fly south or north (return). Internal rhythm or biological clock coupled with environmental changes such as photoperiodism (changing day length- winter days are shorter than night). Most birds also have good map sense so that they reach a specific place in the wintering ground. Map sense is identifying earth features such as mountains, rivers, roads and even shore lines.

Answer 3

Birds can sense the Earth's magnetic field.

There is debate over whether or not they can see some aspect of this magnetic field as a guide.

They know when it is time because instinct tells them to do so.
Temperature change and hours of daylight are two things measured by chemicals in the brain.
When it gets to a certain point, they trigger something that tells the bird its time to move.

Answer 4

from the earths magnetic field. birds have an instinctive sense buit into there brain where they are able to detect the north and south polarities of the earths magnetic field. and therefore, can tell the difference

Answer 5

I think it's because migratory birds have an internal compass & clock. So do we but we don't pay attention to it much because we have all these external things like clocks & calendars and compasses.