I love wildlife, especially birds, and have made a variety of birdhouses throughout my life, but every time I do so I have to look up dimensions or find plans online. To solve this (minor) inconvenience, I made a free, open Onshape document with configurations for common birds in New England, in two different styles. Simply click from the drop down to see the correct 3D model. 

Find the Onshape document here

Find the source where I got my recommended birdhouse parameters here