It has been estimated that Americans spend $3.5 billion annually to feed birds in their backyards. This means during each calendar year somewhere from 0.5 to 1.25 million tons of sunflower seeds, millet, milo, and other seeds are used solely to feed our feathered backyard neighbors.
To put this in perspective, this staggering amount of food closely matches what the United States government sends overseas each year to help alleviate hunger in Africa.
Source: Marzluff, John M. 2014. Welcome to Subirdia. Yale University Press