After a LOT of testing, I have a twist-on perch design I like. I've used this with several species of Pyrrhura conures (greencheeck, blue-throat, maroon belly, etc.), ring-neck parakeets (rose-ringed parakeets), Quakers, Australian grass parakeets, and plum-headed parakeets.

This is sized for most half inch wide cage wires, such as "Chinese breeder cages" referring to the China-manufactured wire cages for small birds, up to to welded or hog-ringed 1 inch by 1/2 inch wire. I have a 9" long perch to fit 9-inch printer beds, and a 10" perch, to maximize length. The models can be resized by 2-5% to adjust to different gauge welded wire, such as 14 GAW vs 12 GAW.

Options (in progress, I'll organize the file names better when this is all done)

I have had my best results printing in ABS, PLA, and PETG (PETG only if the settings are perfect! Loose filament strings are a DANGER!) Bouncing, flying, and landing birds won't shake the perch down, which is common when you buy this kind of design in a soft, injected molded plastic. You may want to slice the model and print just the twist in mount, shrinking or expanding by 0.5% to accommodate printer variation so it grabs the wire well.

The design for normal, vertical wire does not require ANY support material. You may need a raft if your preferred filament likes to pull up and detach from the print bed. If you get really good bed adherence, then save some time and ditch the raft!

For horizontal wire cages, I have a 90 degree rotated perch models, the file "Perch twist on horiz bars needs support.stl" and "twist on perch horiz wire variable width needs support.stl". One is smooth and one is variable width. These two models need an extremely small strip of support material to create a rounded profile.

Be aware that in some cages, the wire may be slightly different than the 1/2 inch spacing, and the perch will not go all the way down to a horizontal wire when twisted into place. In that case, make sure the gap between the horizontal wire and the twist-on perch is large enough for a bird to pull its foot in and out safely and avoid a toe or foot catch.

I would suggest running the top, rounded surface of the perch through the flame of a lighter to adhere all the filament after printing. You don't want a curious bird pulling up a long string of extruded filament and getting their foot stuck under it, or getting it wrapped around their lower beak!

The verticle wire perch design is open on the bottom, so it will not trap the dropping of birds, or water inside a hollow perch. The reinforced bracing keeps the perch sturdy but also lightweight and saves on material. The horizontal perch designs have hollows in them with reinforcing walls... but a lot of slicer softwares just see them as totally hollow. That's fine, use a 10% gyroid fill or a 20% other infill to avoid twisting or bending of the perch over time. Note that the solid perch can collect moisture or particles inside them, so don't place where there is dripping water or regular rain.

As a final safety note, only use light-colored materials for outdoor perches. A dark-colored perch can absorb heat from the sun and become dangerously hot very quickly.

https://www.tinkercad.com/things/lT8HujnVrWn JJ Blodgett has been making some derivative models you can check out, too!