A bird dog certainly does have a predisposition to chase bird and will kill chickens unless trained to accept them and not see them as prey. Since the dog is still young it will have a better opportunity to learn
Your situation is similar to other threads I responded to:
Although it is very true that bird dogs can be very difficult to train not to chase and kill chickens, this certainly can and has been done. You must be able to let the dog spend time with the birds while separated by a fence or restrained on a comfortable lead. He shouldn't be in any position that he sees as punishment though, such as being confined if he in normally not confined. The dog must be able to see the chickens in their natural routines and not just as caged animals. Correct any attention the dog gives toward them immediately. If he looks at them for any more than a couple of seconds in an alert position (ears and body forward) he must be corrected. He will have to learn to lay submissively as they move about. Any chasing or following must be corrected immediately. Finally, when the dog is able to relax while the chickens are moving about you would try letting them together. It would probably take a lot of time (and I mean weeks or months) and careful attention but I think it is possible.
Introduce early and maybe keep them separate by a fence for an extended period. Watch for any attention to the chickens and correct them immediately with a stern voice. There are many people who have plain ole muts that do well with birds, but additional care and attention is necessary. A flighty fluffy bird can be like a toy, even though the dog means no harm. That is one reason NEVER to play catch games with your dogs. You will be rewarding them for predatory behavior. They may not ever be trustworthy enough to leave unsupervised but you may be surprised.
We successfully reconditioned a wild dog that killed to eat and hunted to survive before we started feeding her. I never had to use any force more than one time in the beginning when she went for the birds and I put her to the ground in staunch disapproval. After that I would just growl or say a sharp "Hey!" if I saw any unwanted attention. Eventually we let the birds free and the dog never harmed them, even when we were not present. I think if a wild dog can be reconditioned, almost any dog can.