What is an equation represents the rate at which cats' prey on birds and another represents the rate of Birds Reproduction i The U.S. Data are : In 2011, the ThinkProgress estimated that there is an average number of 13.7 million birds are dying every day in the U.S, 6.5 million of them were killed by outdoor cats every day. It was also estimated a minimum of 10 billion birds breed in the United States every year. This means there is 27 million birds breed every day in the U.S