The Journal Science last fall reported that since 1970 North America is down 3 billion birds. We knew there was a problem. That is over 25% of the population. Only raptors with the elimination of DDT have made a massive recovery (over 200%), ducks and geese and vireos were the other real increase. Grassland birds suffered the most down 50%. If you want to read the rest of the article here is the link.