Keeping down London's pigeon population. Catchers busying Trafalgar Square. Men are work catching pigeons in Trafalgar Square to 'thin out' London's pigeon population. The pigeons familiarity with kindly visitors who feed them is in this case they are doing, for all the catchers are to do is put down food and pick up the birds as they eat it. The pigeons are placed in cages. Photo shows, Mr W Dalton and his two sons, the pigeon catchers, placing pigeons in the baskets. 6 December 1937