Ned,

It's the ducklings, and there is no way for them to get out. The
courtyard is closed in on four sides by buildings. So they're stuck
with whatever they can find, which is cement and grass. I will use
the information provided here to try to feed them.

To be honest, you should try to catch them and take them to a
rehabilitator.

Barring that, fix them a place where the geese can't get into, and
feed them cracked corn, and bread chunks.

Lori