He's probably okay but I'd try to catch him and look him over. When an animal owner notices a change in behavior, it might mean nothing or it could be something. I remember a case where a client brought in a peacock because it was quiet and 'being shy'. So the vet looked him over very...
I have a friend's JRTs come visit for rodent control. Here's link on a similar subject: https://www.backyardchickens.com/threads/do-you-have-a-ratting-terrier-on-your-farm-especially-in-northeastern-us.1425561/
Free range chickens need access to cover to prevent hawk attacks. However, some hawks will fly right in to snatch a bird so the safest thing for them is to keep them in a covered run.