Just an update, we have the 2 hens caged on our front porch with food and water.
We thought about culling them, but then as we discussed this further, we felt that if they did have a disease then our flock has already been infected. They were all over our property after they were dumped.
The one hen does have bone showing in her injured neck but seems to be doing fine, no sign of being stressed. We put our standard medication on it, treated it just like it was our own.
We are going to find them a new home. But we will tell anyone who is interested that we do not know the history of these bird and that they could be carriers of a disease.
Thanks for all the advice, I will be putting some kind of signs up around our property. Not sure exactly how I will word the signs, but they will get our message across.
I spoke to our animal warden and we do have the right to protect our flock, and that includes culling any animals that are dumped onto our property.