CBS : Cats kill billions of birds every year and even more tiny rodents and other mammals in the United States, a new study finds. According to the research, published Tuesday in the journal Nature Communications, cats kill between 1.4 billion and 3.7 billion birds and between 6.9 billion and 20.7 billion small mammals, such as meadow voles and chipmunks. Though it's hard to know exactly how many birds live in the United States, the staggering number of bird deaths may account for as much as 15 percent of the total bird population, said study co-author Pete Marra, an animal ecologist with the Smithsonian Conservation Biology Institute........
