Crow Problem in the Kremlin

I do not know much about the ecology in Moscow personally, so this is an interesting dilemma. It stands in stark juxstoposition to cities like London and New York which also have a lot of crows, ravens, pidgeons, and warblers which nest on buildings and so on and which are not exterminated in this way.  What would the queen say about a legion of hawks unleashed on the Tower of London, for example?

At which point should we consider crows to be a nuisance, and is introducing another bird, such as the hawks (trained or not), really a solution?

My guess is they will find it to not work very well, as crows and ravens tend to be adept at fighting off birds of prey. Perhaps they should deploy toy planes?