I get what you mean.... but.....
1. Parrots don't need filters when they live in open air-space because outdoors in the places where parrots live naturally tend to have better air quality (unlike a home where people use all sorts of unnatural stuff inside- captivity is totally unnatural for them). That having been said, birds living near certain factories do die from the chemicals and insecticides etc also kill them in the wild when they encounter them, as does smoke from wild-fires and extreme pollution.
2. Birds DO eat things that are harmful for them all of the time (and die from it). It happens very commonly--especially in captivity where they are exposed to more dangerous temptations than would be available in the wild.
3. Birds in the wild have a different immune system because of the fact that they survived a lot when they were young (many died and didn't make it to adulthood). Survival of the fittest-------you only see the ones that survive, but MANY wild birds die on a daily basis. Breeding, captivity and veterinary intervention allow young birds to survive things that would kill them in the wild. A bird in captivity gets antibiotics for infection, while a bird in the wild would either die, or survive if lucky...Captive birds have different internal flora and less resistance to bacteria etc. They also do not eat the same diet that they would have in the wild. For my bird to do that, I would need to live in Indonesia and we would have to drive 40 miles a day while making stops for her to forage along a 40 mile path (as she would in the wild). Not possible. Similarly, the humidity etc in a home is not the same as it would be in their native/outdoor environment....Nor is the climate or even lighting (sunlight vs indoor lighting changes A LOT of things----including bacteria etc).
4. Outside of this forum, I find that most people are unconscious of their birds needs (health, mental, housing etc).
5. Birds in the wild often die well before their life expectancy (due to disease, famine, climate, and human interference). To say that they survive in the wild is to negate the thousands that don't survive in the wild. Unless you are scouring the forest floor for dead birds, you aren't going to see the dead ones.