Make sure to check for the hole size before cutting/drilling the hole.
Specify WHICH type of bird you want to attract to the house, then go on-line and find a listing of bird type
and the hole sizes they prefer. Too big and you get different types of robber birds. Really large houses
with correspondingly sized holes may draw in ducks.
IF all else fails and you cannot locate what you need to check hole sizes try the Indiana Gourd Society's
Education Articles here: http://www.indianagourdsociety.org/education.htm
Make a successful birdhouse using the right dimensions.