you can treat by dipping or dusting or spraying. Permethrin is the insecticide of choice.If you dip the pigeon into a solution like malathion, dip only as far as the ears. Don't allow the birds head to go under water. Feather Lice Dust -- (Replacement for Insectrin G.P. Poultry Dust or Zipcide Dust) – Shaker can. Most of your farm stores or home and garden centers should carry this product.Your pigeon will evenetually molt its current feathers and new feathers will grow in there place. Spraying the loft is also a good idea.
Many of the pigeon supply houses carry bath salts. They are rather inexpensive. Add the bath salts to the bath once a week and your pigeon will have soft silky lice free feathers.