Unwanted Tenants. Don't let your birdhouses become homes for Starlings or House Sparrows! These birds were introduced into the contiguous United States from Europe during the mids and early 1900s. Both species spread throughout North America and have become serious agricultural and urban pests. In addition, both species compete with native North American birds for cavity_nest sites and thus may harm native bird populations. For example, nest site competition by Starlings and House Sparrows has been blamed, in part, for the population declines of the Eastern Bluebird, a cavity_nesting bird.
What Attracts Birds to a House? Just as home buyers look for specific features when house shopping a large kitchen, enough bedrooms, garage size, etc. birds also need certain features in their houses. Factors that affect which birds will use a bird house or nesting box include; Entrance hole size, Overall cavity depth and house height, Interior floor dimensions, General house shape and design, Materials used, House location and mounting style.