I'm designing and building a bird feeder for my wife (and I'm a newb at this; if I can do it, so can you). It's still a work in progress. This was done in Tinkercad.

Housing
The core housing is made from 4-inch PVC (schedule 20 I believe, so it's not made for pressure), with 1-inch holes drilled for feeding/perches. You should be able to find 4-inch PVC at your local hardware store - for less than the price of a single bird feeder you can get 10 feet. Cut to whatever length you'd like (though I'm not sure the glue on the bottom could handle a huge amount of seed weight). Drill 1-inch holes evenly spaced in the pipe, and be sure that there are several inches vertically between them. I recommend staggering them around the pipe. Also, drill two small (<1 cm) holes near the top, directly opposite of each other, for hanging.

Prints
The remaining parts are all designed and printed. If printed in the orientations shown you shouldn't need supports. I drilled holes close to the bottom of the pipe, so I cut the bottom perch in half to accommodate (the regular-sized perch wont fit). If you do the same, use the simple bottom. Otherwise I'd recommend the dispenser bottom.

Assembly
After sanding and painting the PVC pipe, use super glue to attach all the parts (bottom on the bottom of the feeder, perches at the holes). The roof should not be glued. It's designed to slide off so you can refill. Run your string or chain through the top holes, if hanging. Otherwise you could simply set it outside.

Alternative Bottom
This is a great bottom design for a PVC feeder. It inspired my dispenser bottom design. Check it out:
https://www.thingiverse.com/thing:4134291