"Feral cats and your neighbor's tabby are a serious threat to many birds," the U.S. Fish and Wildlife Service (USFWS) writes in its backyard booklet For the Birds. This page sets the published estimates of birds killed by cats side by side, each with its own basis, area and year, and then lists what wildlife agencies, the Cornell Lab of Ornithology, Audubon, the American Bird Conservancy (ABC) and animal-welfare groups recommend.
Quick read
The best-known figure: a median of about 2.4 billion birds a year in the US, from a 2013 study by Loss, Will and Marra (Smithsonian and USFWS). Its range has been reported as 1.4–3.7 billion and, after a revision, 1.3–4.0 billion.
What every source agrees on: keeping cats indoors, on a leash or in an enclosure ("catio") protects birds; bells do not.
In the yard: keep feeders and baths out of easy pouncing range of shrubs and decks, where cats hide.
The estimates side by side
The figures below are not averaged or merged; each covers a different area, method or year.
| Estimate | Area and cats counted | Basis | Year | Birds killed per year |
|---|---|---|---|---|
| Loss, Will & Marra, Nature Communications (abstract) | Contiguous US; free-ranging domestic cats, owned and unowned | Model built from earlier predation studies and cat-population estimates | Jan. 2013 | 1.4–3.7 billion (no median in the abstract) |
| Same study, ABC news release (updated) | Same | Revised estimate | Released Jan. 29, 2013, later updated | 1.3–4.0 billion; median 2.4 billion |
| USFWS, Top Threats to Birds | US | Loss et al. 2013a | Data "as of 2017" | 1.4–3.7 billion; median 2.4 billion |
| Cornell Lab, outdoor cats FAQ | US | Loss et al. 2013, called conservative | Undated | 1.3–4 billion |
| Blancher, Avian Conservation and Ecology | Canada; about 8.5 million pet and 1.4–4.2 million feral cats | Estimates from pet and feral cat numbers; over 95% of them fall in the range | Dec. 2013 | 100–350 million; 2–7% of birds in southern Canada |
| Wisconsin study, reported by UW–Madison | Rural Wisconsin; probably over 1 million free-ranging rural cats | Range of kill rates and cat numbers | Reported Mar. 1997 | 8–217 million; best estimate 39 million |
| Older wording (Cornell 2009, Audubon 2010, Illinois DNR) | Not stated (Illinois DNR: US) | Not stated | 2009–2010; Illinois undated | "Hundreds of millions" |
The same 2013 study estimated mammal deaths at 6.9–20.7 billion a year (abstract), revised to 6.3–22.3 billion with a median of 12.3 billion (ABC). The Smithsonian notes that most of these are native mammals such as shrews, chipmunks and voles, and Audubon reported that about two-thirds of the birds killed are native species.
Who does most of the killing. ABC's release says unowned cats (farm and barn cats, strays that are fed but have no home access, cats in fed colonies and fully feral cats) account for about 69% of cat-killed birds and 89% of mammals. Cornell's FAQ says the model behind the estimate assumes 30 to 48 birds per unowned cat per year, with a lower figure for owned outdoor cats.
Compared with other threats. In the USFWS table, cats (median 2.4 billion) are followed by building glass (median 599 million) and vehicles (median 214.5 million); the median for all listed threats together is about 3.3 billion. USFWS adds that habitat loss is thought to be the greatest threat overall but is too hard to put a number on. Glass is covered in window collisions.
Where the figures disagree
- The range moved. ABC's release carries a note that bird mortality "changed from 1.4-3.7 billion to 1.3-4.0 billion" and mammal mortality from 6.9–20.7 to 6.3–22.3 billion. The USFWS table and the study abstract still show 1.4–3.7 billion; Cornell's FAQ uses the revised range. The 2.4 billion median appears in both versions.
- Owned or unowned? ABC's indoor-cat solutions page says "Owned, free-roaming cats kill an estimated 2.4 billion birds in the U.S. each year." ABC's own 2013 release on the same study attributes about 69% of cat-killed birds to unowned cats, and the abstract says unowned cats cause the majority. The 2.4 billion median covers both groups.
- Smaller numbers are not always lower estimates. The Canadian and Wisconsin figures cover smaller areas. The "hundreds of millions" wording on older pages predates the 2013 study, whose authors, as Audubon reported, concluded that free-ranging cats "cause substantially greater wildlife mortality than previously thought."
What helps: the recommendations
| Step | Who recommends it |
|---|---|
| Keep pet cats indoors | USFWS, ABC, Cornell, Audubon, Humane World for Animals, Washington WDFW, Missouri MDC, Illinois DNR |
| Outdoors only on a leash or harness | USFWS, ABC, Cornell, Illinois DNR |
| A catio or other outdoor enclosure | USFWS, ABC, Cornell, Audubon, WDFW, Illinois DNR |
| Spay or neuter; never release or abandon a cat | Cornell, WDFW, Illinois DNR, UW–Madison |
| Don't feed strays or cat colonies | Cornell, WDFW |
| Don't rely on a bell | USFWS, Cornell, Audubon, MDC, WDFW |
Indoors. The USFWS calls keeping cats inside "the best deterrent." Cornell's FAQ says outdoor cats live less than half as long as indoor cats on average, and it suggests play, a second cat as company, a catio or supervised leash walks. Audubon (2010) adds toys, interactive play and window views of feeders for indoor cats, and says kittens are easiest to train to indoor life, though older cats can adjust.
Catio basics. Humane World for Animals describes catios ranging from a window box to a room with a floor and roof. Its checklist: no openings a cat could squeeze through, "even on top"; nothing that might snag a collar; a roof strong enough for local snowfall; fresh water and a litter box or easy access to the house; ventilation and a cozy retreat from cold, rain and sun; and a spot you can see from the house. Where coyotes, bears or other large predators live, it says a catio may not suit unless it is extremely sturdy, and it advises supervising cats while they use it. ABC's solutions page also lists cat-proof fence conversions and free-standing enclosures.
Bells and bibs. USFWS says bell collars "offer birds little protection." Cornell says bells, cat bibs and similar items "typically do not eliminate successful hunting," and its 2009 article notes that cats learn to move without ringing the bell. MDC says a bell usually rings only at the final pounce.
Feeder and bath placement around cats
Cover cuts both ways: shrubs give birds an escape from hawks (see hawks at bird feeders) but give cats a place to wait. Cornell notes that cats "often lurk in shrubbery near feeders and birdbaths," and that ground-feeding and ground-nesting birds and fledglings are at greatest risk. The sources' distances:
| Source | Feeders | Bird baths |
|---|---|---|
| USFWS, For the Birds (rev. 2001) | Away from brush piles and shrubbery that give cats cover | — |
| Humane World for Animals | At least 12 ft from grass and shrubs, within 15 ft of trees; or on a wire at least 8 ft up between two trees at least 8 ft apart | — |
| Cornell, Where to Put Your Bird Feeder (2009) | About 10 ft from cover "seems to be a good compromise" | — |
| Washington WDFW (2000 release, archived) | In an open area where birds can spot approaching cats | — |
| Penn State Extension | — | Near shrubs or low branches for escape from hawks; a ground-level bath where birds can see a predator coming, typically 10–15 ft from the nearest hiding spot |
| Missouri MDC (1999) | Trim bushes near feeders, baths and birdhouses; enclose the space under porches and decks, or move feeders away from it | Same |
Under the feeder. Humane World for Animals suggests a metal cone predator guard on the pole (wide end down), a circular fence about 2 ft high and 4 ft across on the ground below the feeder, sharp-edged gravel underneath, a spill tray, and a motion-activated sprinkler or ultrasonic device for visiting cats. It also says not to leave cat food out around the clock, which attracts more cats. More on setups by feeder style: bird feeder types and the bird bath guide.
- Catio: a screened enclosure reached from the house, with no gaps, even on top, and a roof strong enough for snow (Humane World for Animals; enclosures recommended by USFWS, ABC and Cornell).
- Deck or porch: enclose the space underneath so cats can't hide there (Missouri MDC).
- Pole feeder with a metal cone predator guard, wide end down (Humane World for Animals).
- Low circular fence under the feeder, about 2 ft high and 4 ft across (Humane World for Animals).
- Shrubs and tall grass: cat cover. Feeder at least 12 ft away (Humane World for Animals); trim bushes near feeders, baths and birdhouses (MDC).
- Ground-level bird bath: typically 10–15 ft from the nearest hiding spot, where birds can see a predator coming (Penn State Extension).
- Tree within 15 ft of the feeder, where birds can flee from hawks (Humane World for Animals).
- Nest box on a metal pole, the hardest mount for predators to reach (USFWS).
Nests and fledglings
USFWS says nesting birds, fledglings and birds roosting for the night are "extremely vulnerable to cats." Its booklet notes that nest boxes on metal poles are the hardest for predators to reach and that a sheet-metal guard on a tree trunk may deter less agile cats. MDC gives one size: a sheet of metal about 3 ft tall wrapped around the trunk, its bottom at least 5 ft off the ground. MDC also advises keeping cats inside while young birds are learning to fly and listening for alarm calls in spring and summer. Box sizes and mounting are in birdhouse dimensions; if a cat has caught a bird, see found a baby bird, which covers when to call a licensed wildlife rehabilitator.
When it is a neighbor's cat
Audubon (2010) suggests a motion-activated device that sounds an alarm and sprays water, and a motion-triggered camera to confirm which cat is visiting. Humane World for Animals lists motion-activated sprinklers and ultrasonic devices near feeders. Cornell's FAQ also suggests talking with neighbors about responsible pet ownership.
Checklist
- Pet cats kept indoors, or outside only on a leash or in a catio
- No bell relied on as protection
- Feeders out of pouncing range of shrubs, brush piles and decks (12 ft or more by one source's measure)
- Ground bath 10–15 ft from the nearest hiding spot
- Bushes trimmed and deck undersides closed off near feeders and baths
- Cone guard on the feeder pole; nest boxes on metal poles
- Cats kept in while fledglings are on the ground
- No cat food left outdoors
Sources
- The impact of free-ranging domestic cats on wildlife of the United States — Scott R. Loss, Tom Will and Peter P. Marra, Nature Communications 4:1396 (2013), abstract via NASA ADS
- Same paper, record in Smithsonian Research Online
- Cats kill 2.4 billion birds annually (2013 note) — Smithsonian Insider
- Outdoor Cats: Single Greatest Source of Human-Caused Mortality for Birds and Mammals, Says New Study — American Bird Conservancy (Jan. 29, 2013, updated)
- Solutions for Indoor Cats — American Bird Conservancy
- Threats to Birds — U.S. Fish and Wildlife Service
- For the Birds (booklet, revised 2001, PDF) — U.S. Fish and Wildlife Service
- FAQ: Outdoor Cats and Their Effects on Birds — All About Birds, Cornell Lab of Ornithology
- How to Deal With Unwanted Yard Visitors: Squirrels, Cats, Bugs, Hawks, and More — All About Birds, Cornell Lab of Ornithology (2009)
- Where to Put Your Bird Feeder — All About Birds, Cornell Lab of Ornithology (2009)
- Report on the 2013 cat study: cats pose an even bigger threat to birds than previously thought — Kate Yandell, Audubon (Jan. 30, 2013)
- Lock Up Your Cats! Do It For The Birds — Rene Ebersole, Audubon (Dec. 17, 2010)
- Estimated Number of Birds Killed by House Cats (Felis catus) in Canada — Peter Blancher, Avian Conservation and Ecology 8(2):3 (2013), via DOAJ
- Free-ranging feline terminators take heavy toll on rural wildlife — University of Wisconsin–Madison CALS (Mar. 30, 1997)
- Feral and Free Ranging Cats on IDNR Owned or Managed Properties — Illinois Department of Natural Resources
- Love wild birds? Keep your cat indoors — Washington Department of Fish and Wildlife (news release, June 6, 2000, archived)
- Cats on the Prowl — Joan McKee, Missouri Conservationist (June 1999)
- How to Keep Cats From Bird Feeders and Protect Birds — Humane World for Animals
- Catios: Safe Outdoor Enclosures for Happy, Healthy Cats — Humane World for Animals
- Water for Wildlife: Bird Baths and Backyard Ponds — Penn State Extension