First off don’t even go to pickup a bird unless he as already rounded up and enclosed. Or your just wasting your time.
If the birds are free range you’ll need someone to feed the bird around a garage, shed or even dog pen with top on it. Then put some food inside so he’ll get used to going in. I’d put a perch in there also, he may use it so not be in a rush to come out when he goes in to feed. Now when he is used to going in he will relax a little. Don’t rush him if you try to close the door while he is still on edge he may beat you to the door and you’ll never get him to go back in again. Rainy days are the best days to do this has peafowl like to get under cover rather than getting wet.
Once enclosed before you catch the bird to put him in the box I would say you must be very careful he thinks your going to hurt his so he is not going to let you just walk over and pick him up. Having said this he isn’t going to attack you. Just react to what ever you do to him. The best way to get hold of the bird is to through a large coat or thick blanket over him or better still use a net like a fish landing net. Then drop down on him so he can’t move. Remember these birds aren’t used to being picked up so the first thing you need to do while he is still on the floor is get hold of both legs in one hand. These are what he uses to protect himself and he can badly scratch you or even take out your eye if he starts to strudel to free himself and you don’t have a good grip on his legs. You notice I said both legs if you only have one the bird can spin using his wings. This can end up with you breaking his leg because you wont react quick enough to shop him and your instinct is to grip tighter not let go so he ends up with a broken leg! When you have both legs pick him up by them and let him hang by his feet if you want to check him over before boxing him up then place your hand under his chest and lift him up still keeping a good grip on him feet at all times. Beware of the spares on cock birds even I have draw brood when I have gripped the feet and felt them go into my hand. To transport birds I use a cardboard box not much bigger than the birds body. Put a piece of carpet or hard board in the bottom to stop him from wetting it and going through the bottom of the box when you pick him up then put some saw dust or shavings in to help keep him clean while on the move. If he still as a tail then cut a hole in one end of the box just big enough for the tail and about 3 inches off the bottom. So his legs hit the back if he tries to back out. Keep the bird cool and make air holes in the sides and top. I use a box and not a crate for part wild birds because it’s darker and this helps stop them from stressing, and I don’t give them any room to move around for the same reason and also so they don’t hurt themselves trying to get out. Remember birds don’t move in the dark they think it’s night and if they cant see anything then they feel safe. If the bird is kept cool then he’s good for 24hrs. We’ve shipped hundreds of Peafowl around the UK like this in the last 30 years and only had 2 die when the van they where in was in a road accident and a vet was called in to put them down. Beware when letting birds out into their new pen. Don’t just open the box or they may fly straight up to the top of the pen and hurt or even kill himself. I know someone who this happened to so this is why I’m telling you to roll the box on it’s side then open the top so the bird is thinking more about getting upright more than it is about escaping. Now you leave the pen and the box in it. By the time he’s up on his feet he should walk out looking at what is new home is like. Have water and food already in the pen so you can let them settle in without you disturbing they for a day or so. If you get back home late at night with the birds then keep them in the box until morning then let them out. Just check on them once in a while to see they have settled after their trip.