A difficult little bird to like

Young house sparrows, like the one pictured above, often make themselves at home in our bluebird houses. I can't help smiling at the somewhat comical expression on the face of this bird; however, I am not particularly fond of them. Not only do they take possession of the nesting boxes we have purchased specifically for bluebirds, they are less than friendly toward those same bluebirds, chasing them out of their boxes and sometimes killing them in the process. The bottom line is that, as cute as they look, this is one bird I do not welcome to our backyard buffet. I'm wondering if any other bluebird lovers have had experiences with house sparrows?