For those who love bluebirds, the sight of a house sparrow eyeing a bluebird box is both maddening and frightening.
House sparrows are cavity nesters, just like bluebirds, but they are far more aggressive. They are so territorial that they'll claim multiple boxes and exclude all others from nesting even though they can't possibly use them all. What's worse is that male house sparrows will kill adult bluebirds inside the nest box and peck the chicks to death as part of this territorial behavior.
Many are the sad stories of house sparrow attacks and dead baby bluebirds. Beakless Bluebirds and Featherless Penguins by Sister Barbara Ann tells of the success she had in raising two beakless bluebirds who survived an attack thanks to her care. Not everyone has the time or skill to do this.
As bluebird monitors will tell you, there is no real way to exclude house sparrows because they are nearly the same size as bluebirds. The only effective method is to trap every house sparrow and remove it. It is illegal to trap native birds without a permit, but house sparrows are non-native and invasive. They can be trapped and removed.
Right now is bluebird nesting season. It's time to trap this house sparrow.
Hey you, House Sparrow! Get away from that box! Don't you even think of it!
(photo by Bobby Greene)