Re: Why do pigeons move their heads when they walk?

It's a good thing you figured out that pigeons move their neck for the 
same reason as why we move our hands while walking.
Basically, we move our hands while walking to keep our balance. The 
principle behind this is the centre of gravity of our body. When we walk, 
because of the movement of the legs, the centre of gravity of our body 
tends to shift. This can lead to an imbalance finally resulting in a fall. 
The movement of the hands counters this imbalance and hence we walk 
upright. 
In our body, the head being heavier than the remaining parts of the body, 
the centre of gravity is located more towards the top, than exactly in the 
middle. Similarly, for pigeons, their head weighs less than the 
remaining parts of the body, and so the centre of gravity shifts towards 
the tail. In order to prevent them tipping over backwards, they move their 
necks to gain proper balance. If you might have noticed, other birds which 
do not move their necks, will tend to waddle like ducks while walking. 
This is also for the same reason.
Well, one more thing. If you do not know what centre of gravity is, in 
simple terms, it is an imaginary point where the whole mass of a body is 
concentrated. For more info, look up the MADSCI archives and library.