Currently demarcated as an ecological reserve, the area surrounding the Nabor Carrillo Reservoir is inhabited by native birds year round and migrant birds during the winter. According to some avifauna experts who have studied the birds resting in the trees, this spot in the Valley of Mexico is the most important in the area for birds in migration. Thousands of these animals—mainly ducks like the greater scaup, the blue-winged teal, the brown teal, the ruddy duck, the pintail, the American wigeon, and the canvasback—rest on the water of this reservoir in groups of a couple hundreds, floating, making it their home for a few months.
Migrations are processes of long aerial journeys, implying sometimes flying over uninterrupted stretches of ocean and deserted land. The flight periods are long, and with short rest stops. Flocks of birds arrive each year to the same spot, certain that they will return the next, knowing somehow that the following generations will traverse exactly the same path: thousands of miles covered only to fly back. [...]