Putting An Animal Down

Directly or indirectly?
I have killed some baby mice that were starved and abandoned by there mother just to spare them from the starving death. Also killed some old chickens that were blind and very old.

Indirectly killed our rabbit by letting it out of it's cage during summer and letting it run free as it was old and probably would die that summer anyway. It stayed in our garden for about a month and a half and we feed it but later it disappeared. Probably died as it was very old.

After one of our Budgies died we had one left and it wasn't really a happy pet tbh as budgies need other birds to live with.
After a while we started realizing that it also had very bad eyesight that kept getting worse. At the end it rarely left the cage and when it did it had no idea where it was going and just bumped into stuff. Sad to see it go as i really enjoyed having budgies. Wish the rest of my family wanted to get new ones :C