I think I am right if I say that Plaça Catalunya is, for the people of Barcelona, a place we don't usually stay very long. In the old days, before the walls of the old city were demolished, there was a big space where markets took place and the paths to the towns in the vicinity started. Later, when the Eixample was developed, that area was occupied with cafés, theaters and fair stalls. Actually, the square was the scene of political and literary gathering for many people from Barcelona before Civil War broke out. Now, however, we hardly stay there for more than some minutes, unless there is a concert or a demonstration.
Perhaps there is another circumstance under which a Barcelonian would stay for a while in Plaça Catalunya: as a child, chasing (and sometimes also feeding) the pigeons. I have to say I am not a big fan of urban pigeons, that are a plague in Barcelona, transmit diseases and damage street furniture and fixtures. If I have to choose an urban bird, I prefer Argentine parrots, as I already commented.
Anyway, beyond my preferences, I must admit that pigeons form an very typical image of the city.
Ah, and one final curiosity: it seems that pigeons were introduced in Barcelona for the Universal Exposition of 1929, by a police chief that thought that the image of Plaça Catalunya with pigeons would be much more attractive! I don't think he was aware of how they were going to spread.