After designing and prototyping my latest corexy and delta printers, I had a lot of old empty spools of filament. How sad that they were destined for the landfill. So, I decided to try and make them useful, without using too much filament in the process.

Most filament spools are about 200mm x 60mm. This will serve as a sleeve to close them off and let you use them as birdhouses for small birds. According to the below linked article, the approximate ideal size entrance hole for smaller birds is, on average, close to 30mm, which is the size I chose for this. If you want to request a different size, please comment and I'll be happy to make something else, whether it's for a different spool or different bird. I like the idea of serving nature instead of destroying it very much.

My spools have three spots where the filament can be tucked through the holes for storage. That makes three places to run some lock wire to hang this in a tree, around 5-6' off the ground.

Any potential wind/water egress holes in your spools can be sealed off with weatherproof tape or epoxy.

Total material used should be close to 100g. PETG is the best for outdoor+water resistant things, 0.2 layer height for best water resistance. You can add carnuba wax to the top to help seal it if the 5-6 layers don't do the job.

I'm including a cute little S-Hook that I made which needs to be scaled up depending on the diameter of the branch you want to hang this from. Also should use PETG for that for best UV resistance.

(Link)
https://www.thespruce.com/bird-house-hole-sizes-386641