Birds and the environment

So here are just a few more things that are interesting about birdhouses and the environment:
1.) Attracting birds can act as a pest control:
for people who dislike some insects having birdhouses attracts birds who eat certain species of insects ( birds don't eat earthworms)
2.)Allowing a place to nest for birds can prevent species from going extinct
3) Attracting different types of birds to one are can result in an interbreeding of different species