This birdhouse is for a small birds. The hole is 28mm.
Birdhouse's main body is divided to 6 parts making it very easy to print and each part can be printed within 2 - 5 h using 0.3 layers.
Parts can be glued together or use four 3 mm metal rods in each corner to get a super strong main body.
I suppose this design has been 'approved' as the Eurasian blue tit now nest in it. :)
Use PETG for parts. Infill 15% and 0.3 layer.
The author hasn't provided the model origin yet.