As-Salaam-Alaikum. Today I saw a stray cat hunt down a Pigeon and ate it.I could had save the bird but I didn't because I didn't know what to do.Next time if I encounter the same situation should I feel sorry for the bird and rescue it or let the cat eat it.
All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
You are neither obliged to save that bird nor feel sorry because the cat ate it.
You are not Islamically required to follow the animals that eat others and interfere in that.
Life on earth and the ecological balance in it is based upon what Allah created animals that some of them eat others.
Allah knows best.
You can search for fatwa through many choices