The most humane thing you could have done was put it out of its misery. I know it's really sad but I'm sure it would rather die a quick death then die of dehydration or starvation which could have taken days. If it is still alive just end it's misery in the most humane way you can think of. Sorry. I know it can be hard. But it will be better off for the poor little bird.

Today I found a wild bird with a broken neck. It was not paralyzed because it could walk and it tried to fly away also. I have no idea what breed of bird it was or how long it had been there. I came back 3 hours later to find it about a foot further away from the sidewalk where it was today and it was alive. Any help would be appreciated. I know it's probably dead by now but is there anything I could have done?