HELP

My rooster is bleeding out his anus and we have no idea why.
The Hens all seem to be pecking at it as he shakes his head but we aren't sure what to do.
We've had chickens before and they did fine.
We've had him for about 3 months now and he's been fine but now somethings wrong.
An ideas on what happened and what I need to do or do I need to put him down ?

Welcome to BYC - so sorry you are joining in an emergent situation.
The first step is going to be to isolate your rooster -- separating him from the flock will a) protect him from further damaging pecking from the other birds (they can, literally, eat another bird to death once blood is drawn), b) allow for you to be able to provide treatment to the rooster and monitor his condition more easily, c) allow for you to be able to take any steps necessary in the coop to cleanse the coop and prevent further exposure of the rest of your birds (depending on what we determine to be the issue). He needs to be in a "hospital pen" -- quiet, dark, warm -- either in the house or in a building separate from the flock where you can have easy access for regular monitoring.

Where did you get the bird from?
Once you have him isolated monitor and describe his waste output and food/water intake - these are key in assessing his condition and can provide clues to the cause.
Pick him up and examine him to see if you can detect any wounds, masses, etc in and around his vent - both those caused by the pecking and what may have caused the bleeding and pecking to start.
Are you familiar with the signs of internal parasites? If so, is the bird showing any signs of these?
You mention head shaking - is he doing that in response to the pecking or even when not when his anal area is being pecked?

Greetings from Kansas, dan2red, and ! Pleased you joined us. Ol Grey Mare gave you some great ideas - the best of which is to isolate him from the others as they will just keep picking at him. Then give him a thorough exam. If you can't determine what might be happening, be sure and post your issue in this thread: https://www.backyardchickens.com/f/10/emergencies-diseases-injuries-and-cures
Best wishes and hope you get him on the mend soon!

Welcome to BYC! It's great to have you. You've had some good advice above.

Hello there, and welcome to Backyard Chickens! Sorry to hear about the big guy though. If you determine that the other chicken's simply pecked at him and there is nothing else wrong with him, I wrote an article on wound care for chickens, it might help you taken care of the wound before he goes back out with the rest of the flock. Here is a link to it:https://www.backyardchickens.com/a/wound-care-for-chickens. Good luck with him, I hope you enjoy BYC as much as I have!

Welcome to BYC! I'm glad you joined us!

Hi and Glad you joined us! I am very sorry about your rooster! You have been given some great advice so I will just say have a great time on here and best wishes!