According to a question from the Green group:
Darren Johnson: Have you given consideration to the pigeon control method used by Augsburg City Council which consists of providing pigeon lofts for the city's pigeons and controlling population levels by replacing eggs with dummies (whilst discouraging feeding by the public?). Given the success of this scheme in reducing pigeon populations locally, might it be employed in parts of London, such as Trafalgar Square?
Ken Livingstone: Yes, but the ideas were rejected for a number of reasons including cost and the lack of long term effectiveness.
The measures taken by the Authority has resulted in the pigeon population of Trafalgar Square being the lowest since the Authority became responsible for the square in 2000. The byelaw being introduced by Westminster City Council will mean consistent enforcement across the whole of the square and even greater reductions in the current population.
So affordable housing for pigeons is off the agenda for now...