Okay, I found it. I cut and pasted from threehorses's thread, so this is all her quote:
"For others, here's the best description of it that I've read.
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Source:
http://msucares.com/pubs/publications/p1276.htm
Text:
Euthanasia
Starting a flock treatment early often saves more birds than delaying treatment until the first birds die. For disease diagnosis it is often best to kill a sick bird showing typical symptoms of the flock. Healthy birds from a sick flock contribute nothing when examined.
The most humane methods of killing the bird are injecting sodium pentobarbitol, electrocution, and dislocation of the head from cervical vertebrae. The first two methods are usually too expensive or dangerous for common usage. Cervical dislocation is the most practiced method of killing birds for examination.
To dislocate the head from the vertebra, direct the bird's head toward you. Grasp the bird's head with a handshake grip. Place your thumb behind the head at the base of the skull, all allow the remaining fingers to extend under the throat. Hold the bird's feet with the other hand and stretch the bird until you feel the head separating from the neck vertebrae. You will probably need to bend the head back slightly while stretching the bird.
Be careful to stop pulling when the spine separates or the head may be pulled off. The bird dies immediately when the spine separates.
The killing of small birds such as chicks, poults, or parakeets is often difficult because their heads are small and hard to grasp. The vertebrae may be separated by applying pressure with scissor handles at a joint between two vertebrae. It is best to apply pressure on each side of the neck rather than at the throat and back of the neck. This avoids unnecessary damage to the gullet and windpipe. Large chickens and turkeys may be killed this same way, using burdizzos instead of scissor handles. A burdizzo is a plier-like tool used when castrating cattle and other farm animals."
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