the worst part of the rehab sometimes is having to make the euthanase-or-not call. Sometimes it's a good call, when the bird in question is obviously in a lot of pain - even then, though, there is some debate on whether birds and mammals feel pain in the same ways. Sometimes, as (we think) ethical rehabbers, it's just one of those crappy calls where the bird is non-viable for release although not in obvious physical pain, and we are making the decision not to keep it captive for life.
Had one of each today, without anyone to back me up. A baby pigeon who had had various issues all along for the two weeks he'd been with me, developed crop stasis yesterday and this morning was unable to breathe and gasping frantically for air he just wasn't getting down. And then a mynah that had been shot - a compound fracture of the humerus that was at least a couple of days old. Bits of dried bone sticking out all over, but didn't seem to be in much pain anymore. Just no way to ever put that wing even partway together. And our ethics say that we don't cage amputees.
As volunteers we are never expected to euthanase anything. Some people never do. Some, like me, draw lines in the sand. I won't euthanase a bird with trichomoniasis unless it is clearly very close to a lingering death. I will only do it when there is physical cause and I really believe that I am doing the best for the bird, and often I will make a vet trip for confirmation.
Some days being the executioner still sucks.....