A study in the journal Nature Communications reports that free-roaming cats kill between 1.3 - 4.0 billion birds per year. According to the American Bird Conservancy, free-roaming cats kill an estimated 2 billion birds per year in the U.S. alone. The Humane Society of the United States acknowledges that allowing cats to roam outdoors can significantly shorten their lives and have an impact on wildlife populations, especially threatened or endangered species.  Outdoor enclosures called catios can be built or purchased to allow cats to enjoy time outdoors while protecting wildlife.  For more information, see the links below.

 https://abcbirds.org/program/cats-indoors/cats-and-birds/

https://www.humanesociety.org/resources/home-sweet-home-how-bring-outside-cat-indoors

https://www.humanesociety.org/news/catios-great-outdoors