Baby bluebird

This looks like a baby bluebird, and, as I surveyed the backyard today, the adult male bluebird was attending to it. I've been worried that the nasty house sparrows had frightened the bluebirds away, but maybe they are still here, possibly nesting in our neighbor's bluebird box instead of our new box this little bird is perched on. I have lots of questions, but the bluebirds aren't giving me any definitive answers. It's a puzzle!