For the older bird, I use a pellet gun at the back of the head at the base of the skull pointed inwards to the middle of the skull.
Death is immediate, the bird may extend its wings and tense its body.
I understand that one day I will be faced with the need to cull. I have read this thread and many others and many suggestions as to methods. This particular one strikes me as one that I am comfortable with. I am afraid of any dislocation/broken neck methods because if you don't get it right/pull hard enough on the first go it could be bad. Anyways, I am comfortable using firearms, cannot use them within town limits (my property), but could legally use a pellet gun. So my big question is this... what velocity gun is needed to ensure that you get the job done?? Clearly you understand that not all pellet guns are created equal in terms of stopping power. Could it be done with one of the hand guns? Does it need to be one of the air rifles that fires with the same velocity as a .22? Let's assume this is for an adult chicken or duck, knowing that if you could cull an adult with it, you could cull a chick/duckling with it, or small things the cat catches and doesn't fully kill, etc. Thank you for your input. I know this isn't the most pleasant discussion, but I understand the value in a mercy kill and feel bad enough about the things the cats/dogs bring to me. I know to be a responsible pet owner that this is a piece of it.
Sometimes, from the front is the only way you can do it though. I trap rats and from the front is usually the only way I can shoot them with the pellet gun. The same with skunks with the 22. I don't want to see their back end at all...lol. (I walk right up to the trap to shoot point blank through the wire, which puts me within spraying distance.)