When I learned about this, I was told that it was "instinct." {"Instinct" continues to be the explanation of choice whenever animal behavior implies too much intelligence.} Instinct, though, wouldn't go very far in explaining how pigeons use human transportation routes to navigate. Pigeons follow highways and take particular exits, likely following many of the same landmarks as the humans driving below.
( Jonathan Safran Foer )
[ Eating Animals ]
www.QuoteSweet.com