Painted Bunting Looking Angry...

I am just a beginning bird watcher, but I think I've figured out something today.  There are a lot of birds that get on the bird bath, and start looking very agitated.  They get all puffed up and lean over to the side.  I had just cleaned the bird bath today before this little bird came by.  I think they are looking at their reflections and thinking there are other birds in the water!!!