https://www.vice.com/en_us/article/evjbbz/north-america-lost-nearly-30-of-its-birds-in-the-last-50-years

An under-examined biodiversity crisis has been creeping across North America for decades, according to new research: the mass loss of birds.

Since 1970, the US and Canada have experienced a loss of nearly 3 billion birds across both native and introduced species, the study found. This amounts to a nearly 30 percent reduction in bird abundance in 50 years, the study says, indicating that lasting damage to the integrity of these ecosystems may happen if we don’t start taking action to prevent it.