From somewhere it has never been
How Does a Pigeon Find Its Way Home?
Migration is a route learned and repeated. A homing pigeon is released somewhere new and still gets back.
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Step 1 of 5
Being taken somewhere new is the hard part.
A migrating bird flies a route it has flown before or inherited. A pigeon is driven a hundred miles to a field it has never seen, let out, and expected to work it out from there.
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Step 2 of 5
First it has to know where it is.
Knowing the direction of home is worth nothing without knowing where you are standing. The pigeon has to place itself before a compass means anything at all.
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Step 3 of 5
The Earth's magnetism supplies the position.
Both the strength and the angle of the Earth's magnetic field change steadily as you travel across the ground. Pigeons detect both, which gives them something like a grid to read a position from.
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Step 4 of 5
The sun supplies the direction.
The sun's position only gives a direction if you know the time, so a pigeon runs an internal clock alongside it. Shift a pigeon's day by six hours and it sets off confidently at ninety degrees to home.
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Step 5 of 5
Smell fills in the rest.
Block the nose of an experienced bird and even that one starts to struggle. Pigeons raised where they cannot smell the wind home badly. The scents arriving from different directions appear to build a rough chart of the country around the loft.
The short version
A pigeon homes by working out where it is from magnetism and smell, then taking a direction from the sun and its own body clock — which is why a shifted clock sends it the wrong way with complete confidence.
Try it yourself
Watch the pigeons in any town square. They fly the same lines between the same roofs every day, which is the memory half of the trick, doing its ordinary work.