Step 1: Materials
First and foremost, you need to find a bird-safe tree or large branch. You will want it to be about 3" diameter at it's base (this measurement isn't critical) with lots of branches and twigs. Select a tree based on your bird- a budgie will need lots of branches with smaller diameter branches, while a macaw will need larger, thicker branches. I made this tree for my Senegal parrot and Nanday conure (medium birds.)
There are many species of trees that are safe for birds to climb on and chew, but unfortunately there are also many, many that are toxic. I selected a beech tree as the tree for my play stand because it is local to me and easy to identify. Please see this list for a selection of safe (and unsafe) trees and woods that you can use in the construction of your gym: http://www.parrot-and-conure-world.com/non-toxic-for-birds.html Be sure you are selecting a safe tree! Also, be sure that any tree (or large branches) you select are pesticide free. I would also advise against trees directly exposed to highway traffic, as they absorb a lot of toxins and, in northern climates, road salts. If you don't have your own land/yard, I would suggest keeping an eye out for storm damaged trees, or asking friends and neighbors if they mind you taking a small tree. The trees that are often just right are "pest" trees anyway, saplings that are not intentionally planted.
In addition to a tree, you will need:
an old office / rolling chair (I bought mine at Habitat for Humanity's ReStore for $16)
a length (2'-3') of 2" or 4" PVC pipe (Home Depot, $7)
a 24" electric water heater plastic drip pan (Home Depot, $10 approx)
Clippers or hedge trimmer (or shears)
pine shims (Home Depot $2.50)
bathroom silicone (I used left-overs from bathroom caulking)
Contact paper or vet wrap (optional)
Quikrete 10 lb. Quick-Setting Cement (Home Depot $7.28)
Dust mask, mixing and measuring containers, water and gloves for Quikrete
Step 2: Preparing the Chair
Every chair is different, so you'll have to do some investigation to determine how to get the seat off. For this chair, there was a little tab at the top of the post that I had to pull out. Once I did that, the seat popped off of the post. Then I flipped the base over, and pulled out another tab to release the hydraulic lift. You won't need the hydraulic lift or the post that the chair seat is on- please recycle these if you can (most are made of metal or plastic.)
Step 3: Cut a Hole in the Drip Tray
Measure the outside circumference of your PVC pipe, and either scribe a measured circle, or trace something the same size- I chose to trace a tape roll that was the right size. Draw your circle onto the center of the tray with a sharpie (or similar.) The center is usually easy to find, as it's marked. Using a utility knife, carefully cut out the hole. Use caution! The plastic on these trays is very thick. When you're done, the tray should be able to slip down over the pipe and post (in the photo, I hadn't yet removed the hydraulics.)
Step 4: Glue the PVC to the Chair Base
Step 5: Quikrete the Base
At this point, the PVC should be firmly attached to the wheel base, and the gaps between them filled with silicone. Turn the unit upright. Mix the Quickrete according to the package directions, and pour into the pipe. This is to add weight to the base and ensure a firm stand for the tree (otherwise the PVC pipe could wobble.) Allow it to cure according to package directions.
Step 6: Trim the Tree!
First, you will want to remove all leaves and trim all branches with shears or clippers so that they fall mostly within the radius of the tray (give or take- this is just to keep your floors clean.) Try to trim the tree so there are lots of interesting climbing options, leaving as many branches in place as you can. Keep the portions that you trim off, as you can use them later.
Be sure to measure all doorways that you will want to move the gym through to see how high the tree can be- then put it in the base, and cut the trunk and top until it is the right height. The base will likely need to be shaved a bit to fit in the PVC pipe.
Step 7: Finishing Up
If you choose, wrap the PVC in contact paper that matches your decor, or vet wrap if you think your birds will nibble it. Use bird safe materials, but it is highly unlikely that your birds will access the base of the gym (unless they spend a lot of time on the floor.) The tray can be lined with bird safe litter (like Swheat Scoop litter, carefresh, etc.) or newspapers for easy cleanup.
Push the tree down into the pipe until it hits resistance. Double check to be sure it isn't too tall, and take a few moments to cut off any branches that are too close to the base.
I used bird-safe pine shims to firm up the tree, as there was a lot of space between the tree and the pipe. Just hammer several down into the pipe until the tree no longer wobbles.
Lastly, using the branches that you trimmed off earlier, you will want to add more horizontal perches. This can be done in several ways. I used bird-safe palm fiber rope and veggie-tanned leather strips that I had on hand to tie the horizontal branches. You can also use stainless steel hardware (MUST be stainless steel if you choose this option.) Add more toys liberally and change them often, and your bird will be in a birdie paradise!
As always, supervise your bird during out-of-cage time and replace toys as needed.