In an earlier post I described how this pair of thrushes are deceived into thinking that they are looking at other birds when they come to the windows of the Bosque reception center. The end result is that they beak the windows with such force, they often bleed from the encounter.
They also leave their feces on the wall of the building, making for a mess. Note the color of the droppings.
These droppings were found on top of the table, which is next to one of the windows. I'm assuming that they were left by the birds, given the same blue color of some unknown fruit. I would also conclude that the seeds are from the same berries and they may make it easier to discover the source.