I am not as sure about nursing, but wildlife veterinary medicine is very competitive. Think about it...how many people DON''T think it would be cool to work with lions and tigers and bears, oh my? Having said that, I believe there could/would be a demand for nursing, as when I did a two week placement with a wildlife vet in South Africa, the vet there definitely relied on his vet assistants/nurses/whatever a lot. (The catch: it is very difficult to get a job there as a 'foreigner'...definitely trying to train their own populace and give them a chance.) Similarly, working in a wildlife rehab the nurses practically/pretty much ran the place. Short of actual surgery, there wasn't too much there from a practical standpoint (admin is different) that the nurse couldn't do. So if it is cheaper to hire a nurse, why not? However pay for nurses doesn't tend to be great for the amount of work you do, and my understanding (though again not an expert) is even less so for those working in wildlife/conservation medicine. I don't mean to be a 'Debbie Downer', just trying to be realistic.
A lot of it, as I understand, at least from the vet side, is getting the experience and breaking into the field. A degree in wildlife conservation (for example) is not enough. You need the practical side and the connections as well.
There is a nurse at the Dick Vet that does a lot of wildlife/conservation work. You could try contacting charitable organizations/conservation groups as well as universities.
Best of luck!