Oh, I'm so sorry!  He has a VERY heavy parasite load!  I think you should go ahead & pull out the big guns & get that poultry dust, and dust him GOOD!  Parasites can kill them, for sure.  He may not last another day unless you get him treated, make sure he's eating and drinking, too.  I would put him indoors...he needs to regain his strength, and there are parasites in your coop to be sure, since that's where he was when you removed him.
Please, please, remove him from the coop and dust him with the poultry dust!  It will do NO good to put him right back in.  If you cannot find the poultry dust, get the seven powder.  Also, you need to get him drinking & eating good, nutritious food & lots of it to gain his strength back.  If you can, stop by a pet store & pick up some Baby Bird Handfeeding Formula - it's loaded with excellent stuff for birds, and high protein - you mix it with water, and you can sort of squirt some over his food to entice him to eat more.  THey love that stuff!  If it's only a parasite issue, you should be able to get him through this!