When I was a kid, my grandfather built a Martin house that could house 16 nesting pairs. He put it up at the head of the one acre garden that the families shared(grandparents,gradfather's brothers family, our family, and my uncles)the martins showed up every year, and helped to keep the bugs controled in the garden. I learned alot in that garden from my grandmother, she was a 5th grade teacher, and loved science. I miss them both.
