comment: >
  
  Probably (really have no idea). I'm guessing dozens of birds in a nest huddled is a big part.
context: Monk parakeets have established perches in Miami, New York and other cities. But the colony underneath the Skyway, where the birds build their nests among the concrete and steel supports several stories off the ground, is one of the more improbable spots they scratch out a living.
  
  Somehow the image of escaped tropical birds surviving and even thriving in the sub-zero conditions of Chicago in winter gives me hope. Hope they continue to thrive! >
  
  On the Northside, there are a bunch in Cell Towers. The last group I saw was along the North Branch. There were a few starting south of Devon (West Rodgers Park), and going north up through Lincolnwood. 
  Not sure how they do it. Their nests are kinda big. >
  
  Do the towers emit some warmth from the machinery?