There is absolutely no doubt that the bird population of the United States is dramatically less than it was a century ago. But, there is no scientific consensus on the cause, and certainly NONE on what to do about it, if anything.
I have been a life-long watcher of birds in nature (not informed enough to call myself a real “bird-watcher). It is clear that in many areas bird populations are at very low levels.
It must be that dastardly DDT that’s causing thin eggshells! //S
Banning DDT was another stupid Gov’t decision that led to greater problems.