Hello, are you asking what causes pigeons to vomit when they eat oregano oil? Pigeons vomit when they eat oregano oil because they can't tolerate the flavor. The main components of the common oregano oil are carvacrol and thymol, insoluble in water, is made in the feed used in the 10% premix, white smooth powder, particle size of 100 mesh or more, with the unique odor of the herb oregano, pigeons very much do not like the taste, so in the feeding will be spit out.