Well, today as I was leaving the same place, I recognized their calls. However, the volume was much increased; I thought that maybe they were on the roof.
Over a hundred green birds with yellow bills and red markings on their heads were hanging on the local trees, and flying off in batches to the east.
I stood there stunned watching them at it for about fifteen minutes. They were beautiful in coloration, but a little awkward in flight. Still, it amazed me that whenever they landed in a tree, they practially disappeared, except for the flash of red on their heads.