External parasite could be fleas, mites, lices, tick. Not easy to tell apart unless under microscope.
Mites are more common external parasite in birds.
Treatment are the same, Natural and synthetic pyrethrum are effective and safe. Ivermectin and moxidectin are effective if they are blood sucking/ keratin feeding parasites (e.g. Fleas. ). Go to a parrot supply store and they should hv some of these chemical spray/wash in store