Hello there,
Bird flue doesn't normally effect song birds in this dramatic of a way, and is generally considered to be non-leathel to songbirds and more effects waterfowl, upland game birds, raptors and mostly domestic poultry. With that said the disease is a virus that changes over time. There is still a chance it could be bird flu, but again I have not heard of it being lethal to song birds.

There are many things that kill birds so it isn't possible to say what it is. There is a chance this could have been caused by a pollutant in your area, or by a pesticide being misapplied. Or perhaps it is a different disease in your area. It may also be a stray cat that is killing your birds (they will sometimes kill but not eat). Or maybe even weather related. I couldn't really say what could be going on here.


With that said you can report these bird deaths to the Michigan DNR. You can learn more about reporting here: https://www.michigan.gov/mdard/animals/diseases/avian/avian-influenza/report-sick-or-dead-birds

You can learn more about avian influenza (aka bird flu) here: https://www.michigan.gov/mdard/animals/diseases/avian/avian-influenza


And more about how it effects song birds and what birds are most impacted here: https://www.allaboutbirds.org/news/avian-influenza-outbreak-should-you-take-down-your-bird-feeders/#