I saw this response at RedState to a National Audubon Society plea to turn off our lights at night and pull down our shades to save a billion birds a year.
[B]ird activists have consistently thrown around another figure related to bird deaths: 3 billion. This number is cited as the number of birds lost on the continent since 1970, with Audubon itself promoting the figure in 2019.
The 2019 number ... implies that 3 billion bird deaths over the span of 49 years is a massive toll ...
We live on the shores of Lake Erie in downtown Cleveland. In May, migratory birds fly north from the tropical south to Canada. These birds have no familiarity with buildings and windows and fly into them, especially at night. Some die but some can be rescued and rehabbed and volunteers go out looking for survivors. It makes them feel good and I empathize with them. Some of these are rare or endangered species so saving these is a good deed. The resident riffraff - house sparrows, pigeons, starlings - never seem to hit windows.
But migratory birds are tracked by weather radar and the numbers are truly astounding. Several billion birds migrate north in spring and return in autumn. They fly at night at very high altitudes and land en route to rest and refuel. Rescuing a few who hit windows is not significant to the survival of the hundreds of species that migrate. Three billion over 50 years is 6 million per year out of several billion per year. That is hardly significant.