Adapted from Jim Conrad's online book A Birding Trip through Mexico, This excerpt from "Mexico City" in México state

The day finally comes when I'm healed enough to take the subway downtown to the Zócalo. The huge Zócalo is the main plaza downtown, Mexico's "Red Square." On its western side rises the National Palace and on the northern the Metropolitan Cathedral. The ruins of an Aztec temple occupy the northeastern corner.  Government offices and upscale stores, especially jewelry shops, line the square elsewhere.

On the Zócalo's acres of pavement today there are gawking knots of tourists, small groups of Indians, unionists and taxi drivers with banners and bullhorns protesting this and that, and of course the whole open area is populated with pigeons, known in field guides as Rock Doves. Here people feed them and little kids run after them, exactly as is done the world over.

In the countryside I've noticed that usually if one bird in a flock suddenly flies up, all the others apparently think that something must have frightened it, and they fly with it. However, here I see that regularly one bird flies up but others just ignore it.

I'm probably noticing this only because I know about Michael Davis's paper published in 1975 in which he described the flight-intention movement of a bird preparing to fly up, and wishing to inform its neighbors that nothing is really amiss.  From what I can see, the movement consists mainly of a very fleeting, subtle crouch and opening the wings a split second before flying up. If launching into the air isn't preceded by this movement, other pigeons fly up with it.

Then I see a piebald pigeon ruffle its neck feathers almost like the Bronzed Cowbird, lower its head and trot in several full circles. This is more pigeon-communication, a gesture known as bowing. It means different things, depending on its context. If it's done near its nest the display is a defensive gesture. However, here the bird is just showing off in front of that white female with brown speckles standing near him. And then a pigeon flies about with much-louder-than-usual wing-flaps. Wing-clapping flight is also an early form of courtship.

I could just watch pigeons all day, but here it's hard to find a good place to sit down, and I need to do exactly that.