text: Some Falcon species like peregrines and probably kestrels use tall city buidings to hunt and nest on as if they were cliff faces. The buidings, like cliffs, act as good vantage points (provide updrafts) to hunt other birds. As long as there is plenty of prey items like feral pigeons (peregrines) or mice to hunt (kestrels) they probably don't have many problems living in cities. Heavy pollution could be a problem?