The number of chickens killed by bird flu is miniscule compared to the amount that have been culled by hyperventilation bureaucrats. Chickens have survived thousands of years without being rendered extinct by a virus, that's not going to suddenly change, because that's how evolutionary dynamics work.
Chickens have survived for thousands of years, but not in quantities and conditions that we cultivate them in today to feed ourselves.
So around the same time as the Spanish flu pandemic?
Sure, in an environment that’s completely different from an industrial farming operation.
If they didn’t cull our poultry industry—as a whole—would be ineligible for export to most countries.
If you think about it, veterinarians are a evolutionary adaptation as well!
Edit: stetrain phrased it better :)
There might be more chickens in one mega-farm than there used to be in the wild in their original homeland in Southeast Asia.
In my country, if any factory farm is hit by any virus, the meat is considered tainted and cannot be sold (wouldn't be bought by big retailers anyway) until the virus is cleared.
For poultry it can means 3 months of throwing eggs away. It's more economical to kill all the chickens and start from scratch. If the contamination reach your neighbours, they will do the same thing (so you want to do it early, and radically).
https://en.m.wikipedia.org/wiki/Marek's_disease
Current strains are hitting 100% mortality rates in unvaccinated chickens, and it can spread over a mile on the wind. Wild turkeys are asymptomatic carriers.
Currently you're just parroting conspiratorial disinformation.
I did a web search for you (it's not difficult, you should try it one day) and this came up: