Complete plans for a wren birdhouse, including its size, materials and a video on how to put them together, is available on Birdwatching-Bliss.com. The plans also lists how to make the birdhouse's entrance size to match the most likely birds that use this kind of birdhouse. A link to instructions for an eco-friendly version is also available on this website. Placement instructions are also posted. The plans were originally drawn up by the National Resources Conservation Service.
Certain types of wrens, chickadees and nuthatches may take up residence in a wren birdhouse. Some specialty species of wren, such as cactus, canyon and marsh wrens, do not use a nest box because they do not nest in cavities, but on cliffs and shrubs.
Wren nest boxes must be monitored because they sometimes attract aggressive and invasive birds such as house sparrows. House sparrows should be discouraged from using this or any other type of nest box built with native birds in mind. When a house sparrow takes over a nest box, it destroys the eggs and kills existing chicks. Likewise, wrens are also known for being extremely competitive about nest cavities and may raid bluebird boxes, though the two species have been known to coexist peacefully in some cases.