interestingly, I have heard knowledgeable people expressing doubts over the presence of pure Lady Amherst's pheasants in Europe or America. The Lady Amherst's that commonly are seen in zoos, are kept in the thousands by private keepers and were the basis for the introduced populations in various parts of the world are the result of lineages started a long, long time ago. Initially relatively few birds were available in the aviculture and information on separating female Lady Amherst's and female golden was not easily available. The females are very similar. The two species breed freely together and the hybrid offspring is fertile. After repeated backcrossing, any obvious external features that easily revealed the hybrid origin were deluted and eventually disappeared. They look like Lady Amherst's and may well be e.g. 95% Lady Amherst's but that isn't 100% pure. Regardless of their pedigree they are stunning display animals.
It is similar to red junglefowl of the wild form where most kept actually have genes from domestic chickens in them. In that species there has been a move by serious keepers to get the bird's DNA testet for purity to weed out any impure specimens from breeding programs.