I did it in reaction to sparrows or the like. I like birds but they should go stand in the shrubs and trees rather than on my door.
An American Robin is a fairly large bird, however, so I didn’t expect to see one on anyone’s window ledge, whether building or not.
Mallards do like to stand on the peaks of our roofs in the development, but when I see one on a window ledge I’ll have seen everything there is possible to see, and more. :)