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It depends a lot on the breed. I am not sure what Burmese chickens are but if they have been roosting high in the treees it will be hard to break them of the habit. 
  You can rig a catcher by nailing a cross piece atop a long board or pole. (The lighter the better). It will look like a T. Then when the chickens are roosting, you gently and slowly push the T end of the pole under the chicken's belly area.The chicken should step up on top of the T. Then as slowly and gently as you can lower the chicken down until they are low enough for someone to grab its feet.
  This is hard to do in trees, especially ones with a lot of limbs close together. It works great in barns when they are roosting on rafters. 
  You can also rig a trap with a pen or coop. Just tie a long rope or string to the door, bait it with corn or whatever and then position yourself where you can pull the string and close the door. After the chickens are in of course. You may only get a few at a time and it will  take time and patience but it will work.
  The third option is to find a good tree climbing teenager, stick a small flashlight in his mouth, give him a burlap  or onion sack, wait till its dark and give him a boost. He won't get them all because some will spook and fly out of the tree but over a few nights he might get most of them. ( If you know any coon hunters, there is usually a designated tree climber among them.)
   If there is a pen or coop the best way is get them used to eating in it and to trap them in there.
  A combination of all these things should allow you to get them all.
Hope this helps, Monty