BJ, we have had pheasants in the US since the 1800s when they were brought here by wealthy sportsmen who hunted them in England. They thrived in certain parts of the US. Why? Because there was great habitat the kind pheasants needed to thrive. The loss of pheasants has nothing to do with mother nature, but it has everything to do with the activity of human beings. If wildlife has what it neede to thrive and reproduce, if not, they go the way of the Dodo. You do know that Chukar partridge are not native, but in certain areas of the US, where they have what they need, that is close to the habit in the countries they came from, they are alive and well. The upside for them is , where they live in the US is not conducive to devlopment and if you are not in excellant physical condition you will not succeed at hunting them. The Hungarian partridge is another introduced species that was introduced and is thriving in some areas of the country. Introduced species have been in the US for a long time, so long that a lot of hunters do not know they were introduced.