We're having similar problems although I'm not sure if it's the orioles, catbirds or grosbeaks doin' the poopin'. My solution is just to put out a few dollops of jelly, just enough to get them through the day, and then wash everything out each night. It helps to have a spare so you can bring the fresh one out each morning when you bring in the dirty one. Maybe that would work for you, too?
"We are--each of us--dying; it's how we live in the meantime that makes the difference."
"It's not what you gather, but what you scatter that tells what kind of life you have lived!"
"Be kinder than necessary, for everyone you meet is fighting some kind of battle."