https://science.sciencemag.org...1126/science.aaw1313

“... we report population losses across much of the North American avifauna over 48 years, including once common species and from most biomes. Integration of range-wide population trajectories and size estimates indicates a net loss approaching 3 billion birds, or 29% of 1970 abundance. A continent-wide weather radar network also reveals a similarly steep decline in biomass passage of migrating birds over a recent 10-year period. ...”

I believe it.

from the Cornell Lab of Ornithology
1 in 4 Bluejays
1 in 3 White Throated Sparrows
1 in 3 Baltimore Orioles
are gone

+50% Waterfowl
+200% Wild Turkeys and other gamebirds
These increases are due to the efforts of sport hunters.
+200% Hawks and Falcons due to conservation efforts such as banning DDT.

I had two chickadees at my suet feeder last winter. That was once. Chickadees are common here in the winter.