| MadSci Network: Zoology |
First of all, let's look at what you mean by "pigeon." Most people, when talking about pigeons, mean the bird scientists call a Rock Dove (Columba livia). This is the blue-grey bird you see all over our buildings and statues, in the hearts of our cities. There are several species of bird that are properly called 'pigeons.' Many of these birds do migrate, short or long distances.
Rock doves are a different story -- somewhat. Undoubtedly some of them do migrate; just as certainly, some of them don't. I know some of them live in Minneapolis all year long, and if you're not going to leave here in the winter, you're probably not going to leave anywhere. And yet, there are reports of rock doves migrating "thousands of miles" (as at this rock dove fact page). So what's the story?
Well, to understand that you have to understand a little about migration. The important question is why do birds migrate? Migration is a long ordeal, and definitely risky. The only reason it would evolve in as many species as it has is if staying behind for the winter is even more risky. Cold is sometimes a factor, but many birds could survive a cold winter. More of a problem is the reduced amount of food. In human cities, however, there's always shelter from the cold, and, more importantly, food is available year round. In this environment, there's a good chance that a resident rock dove will survive the winter, so more rock doves will die if they migrate than will die if they stay behind.
Of course, this is only part of the story. Rock doves were domesticated by people to serve as couriers, homing birds, and racing birds, and this domestication may have weakened the instinct to migrate. Fortunately (or not, depending on your point of view), when some birds escaped and went wild, or "feral," human cities made perfect homes for them.
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