There are some great looking wooden birdhouses, but after just a year or two, they start to rot and fall apart. Even when cleaned out each fall and stored indoors each winter. Wood just isn't very durable, and birdhouses get abused inside and out.
Doing some reasearch, I came across this design that uses PVC pipe for most of the house. However, the ends and perch are still made of wood. Sure, you could use composite lumber, but it's still pretty hard to cut a perfect 4" plug. Plus, I've never seen a composite dowel.
Instead, I designed a door with the following attributes:
- Easy to align and insert into a 4" pipe cut at an angle.
- Easy to glue or screw into place.
- A reinforced perch, because things that stick out tend to get broken.
- A tapered lip to help with water and debris drainage.
- Simple to print with no supports
A full blog HOWTO is here.