Very interesting Dave. (p.s. and may I say congratulations on the link!
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I lived in a different area for a little while at the end of last year and one of the neighbours there had homing pigeons. It was a rural area and hot as hades. Every afternoon at around 3 to 4 pm as the heat of the day was lifting and the breeze came up, he'd let his birds out to fly.

I'd make a cup of tea and sit on the verandah to watch them it so was fascinating. There were obviously younger birds and more experienced birds too. They would change leaders a lot and as the birds changed leaders, I noticed some would drop out and go back to their house. They only flew in a large circle of about 150 metres or so and always in the same direction. Sometimes I'd notice one or two birds would just leave the others and take off on their own.

I always thought it was a strange hobby, keeping caged birds like that, but it was fascinating to watch those birds. They certainly didn't look like the average pigeon. Anyway, sorry about the tangent.