First Paragraph: The common barn owl (Tyto alba) is the most widely distributed land bird in the world (Bunn et al. 1982). It is often called the most beneficial bird in the world because of the hearty appetite for voles, gophers, mice, and rats. Several farmers have observed that gopher populations are substantially reduced when sufficient barn owl nesting sites are present on the farm. Unfortunately, little or no long-term research has been conducted to document an effect on rodent populations by installing nest boxes.