Today is a sad day. I have a flock of four beautiful birds, and when I went out to them today, I noticed that two of them have "bubble eye". This is the third time in three months. I've treated the flock with antibiotics twice before with success, but whatever respiratory illness they have just keeps coming back. I've made the tough decision that I will have to cull the entire flock. This is a decision that I hoped never to face, but now that I've decided, I'd like some suggestions for the most humane way of accomplishing the unpleasant task.