Two-component epoxy
Super glue is the only way.
Elmer's China Glue will work for that.
you go home and die slowly
try a quality super glue, or perhaps gorilla glue. Caulking would work.
Super glue, or take it to a glass-blower and have him 'weld' it with glass.
The glass pro's DO use a type of super glue, especially to fix stone chips in windshields. From the layman's point of view this is difficult as they have special ways of sucking all the debris out of the crack and then forcing the glue in under pressure. It's not possible to do this without special machinery.
It does require some skills to repair a cracked piece of glass in a window, no matter what method you choose. Is it a single crack? Multiple crack? Is the cracked piece in the border or within the main body of the window? If it's in the border area, then it may be easy for you to remove the piece and either repair it or change it. If it's in the main body of the window, it gets tricky. My recommendation would be to bring it to a stained glass repair person. If you decide not to, and the window is not of any historical value then you could just infuse the crack with "Crazy Glue." Just clean the cracked piece with acetone using a cotton swab and make sure you flush the crack well with the acetone. Wait a minute or two, and gently apply the glue starting from the center of the crack and working your way to the edges. Give it a try and if you are not happy with the result, the process is reversible.
As long as the glue is dry before you put them back in. A few months ago, I had bitten my tongue and used super glue to hold the piece in place so it could reattach. No taste, sting or problem.
take it to the fix it man! he should glue it up and sand it off, the crack will have gone it it will almost be invisible if its done well. dont leave it else the crack will expand and the tuning will go!
I would remove the bird from the cage during the repair if possible, then place Krazy Glue or another good adhesive glue in the crack, the put duct tape over the top of the crack to help seal it in place. The fumes from the adhesive may irritate the bird, which is why you may want to relocate the bird until the glue sets (about 10 minutes or so).
A clear epoxy. - Heat it gently in a metal jar lid or similar on the stovetop and then apply quickly with a tooth pick.