Outdoor cats kill 3.6 million birds every day on average in the United States, for a total of at least 1.3 billion birds per year. Cats have even directly contributed to the extinctions of 22 bird species on islands around the world. Researchers in the United Kingdom estimated that 55 million birds fall prey to domestic cats there each year.
Since cats are going to kill birds and since people love cats, the solution is to find a way to keep cats from killing birds. People have tried putting bells on cat collars but cats can often move silently before the bells can ring and alert the birds.
Now a bird watcher named Nancy Brennan has created a collar that uses color. Since birds have excellent color vision, the idea is that birds will be able to spot this colored collar long before the cats can capture the bird.