Dirty Birdbath...

Last year I added a white birdbath to a newly constructed flower bed. Last year the birdbath was in constant use but did not get nearly as dirty as what i am seeing this year. I know that this month has been a whole lot wetter than last year... but the robins aren't THAT dirty. I'm routinely changing brown water. This morning I think i discovered what the cause of all this dirty water is... I glanced out to see a big crow in the birdbath!