DOMESTIC CAT
PREDATION ON BIRDS
AND OTHER WILDLIFE
How many birds and other wildlife do domestic cats kill each year in the U.S.?
Exact numbers are unknown, but scientists estimate that nationwide, cats kill hundreds of millions of birds, and more than a billion
small mammals, such as rabbits, squirrels, and chipmunks, each year. Cats kill common species such as Cardinal, Blue Jay, and House
Wren, as well as rare and endangered species such as Piping Plover, Florida Scrub-Jay, and California Least Tern.
There are more than 77 million pet cats in the United States. A 1997 nationwide poll showed that only 35% are kept exclusively
indoors, leaving the majority of owned cats free to kill birds and other wildlife at least some of the time. In addition, millions of stray
and feral cats roam our cities, suburbs, farmlands and natural areas. Abandoned by their owners or lost (stray), or descendants of
strays and living in the wild (feral), these cats are victims of human irresponsibility due to abandonment and failure to spay or neuter
pets. No one knows how many homeless cats there are in the U.S., but estimates range from 60 to 100 million. These cats lead short,
miserable lives.
Loss of wildlife habitat and fragmentation due to human development are the leading causes of declining bird populations. However,
scientists now list invasive species, including cats, as the second most serious threat to bird populations worldwide. Habitat fragmentation
provides cats and other predators easier access to wildlife forced to live on smaller tracts of land. Rather than havens for wildlife,
these areas can be death traps.
Cats Are
Not
a Natural Part of Ecosystems
The domestic cat,
Felis catus
, is a descendant of the European and African wild cats.
Domesticated in Egypt more than 4,000 years ago, cats may be the most widespread predator
in the world. In the U.S., cats were not abundant until the late 1800s when they were
brought to help control burgeoning rodent populations associated with agriculture. Some
people view cat predation of rodents as beneficial, but native small mammals are important
to maintaining biologically diverse ecosystems. Field mice and shrews are also important
prey for birds such as Great Horned Owl and Red-tailed Hawk.
Cats Compete With Native Predators
Owned cats have huge advantages over native predators. They receive protection from disease, predation, competition, and starvation—
factors which control native predators such as owls, bobcats, and foxes. Cats with dependable food sources are not as vulnerable to
changes in prey populations. Unlike many native predators, cats are not strictly territorial. As a result, cats can exist at much higher
densities and may out-compete native predators for food. Unaltered cats are also prolific breeders. In warmer climates, a female cat
can have 3 litters per year, with 4 to 6 kittens per litter.
Cats Transmit Disease to Wildlife
Unvaccinated cats can transmit diseases, such as rabies, to other cats, native wildlife and humans. Cats are the domestic animal most
frequently reported to be rabid to the Centers for Disease Control and Prevention. Cats are also suspected of spreading fatal feline
diseases to native wild cats such as mountain lion, the endangered Florida panther, and bobcat. For more information, see the fact
sheet,
The Great Outdoors Is No Place For Cats at
www.abcbirds.org/cats.
Photo: Clipart.com
Great Horned Owl
Cat Predation Studies
Extensive studies of the feeding habits of free-roaming domestic
cats have been conducted over the last 55 years in Europe,
North America,
Australia, Africa,
and on many islands.
These studies show
that the number and
types of animals
killed by cats varies
greatly, depending
on the individual
cats, the time of year, and availability of prey. Roughly 60% to
70% of the wildlife cats kill are small mammals; 20% to 30%
are birds; and up to 10 are amphibians, reptiles, and insects.
However, birds can be up to 100% of a cat’s prey on some
islands.
Some free-roaming domestic cats kill more than 100 animals
each year. One well-fed cat that roamed a wildlife experiment
station was recorded to have killed more than 1,600 animals
(mostly small mammals) over 18 months. Rural cats take more
prey than suburban or urban cats. Birds that nest or feed on
the ground, such as California Quail, are the most susceptible
to cat predation, as are nestlings and fledglings of many other
bird species.
The following are summaries of specific studies:
East Bay Regional Park District, CA
:
A two-year study
was conducted in two parks with grassland habitat. One park
had no cats, but more than 25 cats were being fed daily in the
other park. There were almost twice as many birds seen in the
park with
no
cats as in the park
with
cats. California Thrasher
and California Quail, both ground-nesting birds, were seen
during surveys in the no-cat area, whereas they were
never
seen
in the cat area. In addition, more than 85% of the native deer
mice and harvest mice trapped were in the no-cat area, whereas
79% of the house mice, an exotic pest species, were trapped in
the cat area. The researchers concluded, “Cats at artificially
high densities, sustained by supplemental feeding, reduce
abundance of native rodent and bird populations, change the
rodent species composition, and may facilitate the expansion
of the house mouse into new areas.” (Hawkins, C.C., W.E.
Grant, and M.T. Longnecker. 1999. Effect of subsidized house
cats on California birds and rodents.
Transactions of the Western
Section of The Wildlife Society
35:29-33).
San Diego, CA
:
In a study of the relationships between coyote,
mid-sized predators such as cats, and scrub-dwelling birds, cat
owners living along the rims of canyons collected the prey their
cats brought home. These canyons are isolated pockets of habitat
with species that may not occur elsewhere. On average, each
outdoor cat that hunted returned 24 rodents, 15 birds, and 17 lizards
to the residence per year. Birds were 26.7% of the prey killed by
cats. The researchers
estimated that cats
surrounding mid-sized
canyons return 840
rodents, 525 birds, and
595 lizards to residences
each year. This level of
predation appears to be
unsustainable. The study
also found that in small canyons where the coyote was absent, there
was an increase in mid-sized predators such as cats, and a drastic
decline in diversity or elimination of scrub-breeding birds. But in
the larger canyons where coyotes were still present, the scrub-
breeding birds were also present. (Crooks, K.R. and M.E. Soule.
1999. Mesopredator release and avifaunal extinctions in a
fragmented system.
Nature
400:563-566).
England
:
The Mammal Society conducted a survey of animals
brought home by domestic cats. During a five-month period in 1997,
964 cats killed more than 14,000 animals. The mean number of
catches or kills per cat was 16.7, and birds were 24% of the prey.
The mean kill rates for belled cats was 19 and for no-bells 15. In
other words, cats wearing bells killed more. Only 162 rats were
killed by the cats, making them very poor ratters. The researchers
concluded, “Although it is unlikely that cats alone will cause any
species to become endangered in Britain, for those which are already
under pressure for other reasons, such as thrushes, harvest mice,
grass snakes, and slow worms, cats could become significant.”(The
Mammal Society. 1998. Look what the cat’s brought in!
www.abdn.ac.uk/mammal/catkills
).
Wichita, KS
:
In a study of cat predation in an urban area, 83% of
the 41 study cats killed birds. In all but one case, when feathers
were found in scat, the owner was unaware that their cat had ingested
a bird. In fact, the majority of cat owners reported their cats did
not bring prey to them. Instead, the owners observed the cats with
the bird or found remains in the house or in other locations. A de-
clawed cat killed more animals than any other cat in the study. (Fiore,
C. and K. B. Sullivan. Domestic cat (
Felis catus
) predation of birds
in an urban environment.
www.geocities.com/the_srco/
Article.html
).
Wisconsin:
Researchers at the University of Wisconsin coupled
their four-year cat predation study with data from other studies,
and estimated that
rural
free-roaming cats kill at least 7.8 million
and perhaps as many as 217 million birds a year in Wisconsin.
Suburban and urban cats add to that toll. In some parts of the state,
free-roaming cat densities reach 114 cats per square mile,
outnumbering all similar-sized native predators. (Coleman, J.S.,
S.A. Temple, and S.R. Craven. 1997. Cats and Wildlife: A
Photo: Alan Hopkins
Photo: Dr. Gil Ewing
California Quail
Cat catching Yellow-rumped Warbler
Conservation Dilemma. 6 pp.
www.wisc.edu/extension/
catfly3.htm
). In an ongoing, but unpublished, study of cat prey
items including stomach contents, scat analysis, observations of
kills, and prey remains, birds were 19.6% of 1,976 prey captured
by 78 outdoor cats (Temple, S.A, Univ. of WI, personal
communication, 1/22/04).
Virginia
:
Researchers compared a free-roaming domestic pet cat
in a rural area with 4 urban cats. The rural cat captured a total of
27 native species (8 bird, 2 amphibian, 9 reptile, and 8 mammal,
including the star-nosed mole, a species of special state concern).
The 4 urban cats captured 21 native species (6 bird, 7 reptile, and
8 mammal). Between January and November 1990 each cat caught,
on average, 26 native individuals in the urban area, and 83 in the
rural area. The study did not count prey killed and completely
consumed, prey killed and left elsewhere, prey that escaped but
died later from infection or injury, or non-native prey. (Mitchell,
J. and R.A.Beck. 1992. Free-ranging domestic cat predation on
native vertebrates in rural and urban Virginia.
Virginia Journal of
Science
43:197-206).
Cats on Islands
:
Because some island bird populations evolved
in the absence of mammalian predators, they have no defense
mechanisms against them. When cats are introduced or abandoned
on an island, elimination
of entire bird
populations can result.
Domestic cats are
considered primarily
responsible for the
extinction of 8 island
bird species, including
Stephens Island Wren,
Chatham Island Fernbird, and Auckland Island Merganser, and the
eradication of 41 bird species from New Zealand islands alone.
On Marion Island in the Sub-Antarctic Indian Ocean, cats were
estimated to kill 450,000 seabirds annually prior to cat eradication
efforts. (Veitch, C.R. 1985. Methods of eradicating feral cats from
offshore islands in New Zealand.
ICBP Technical Publication
3: 125-
141).
Cats in Habitat Islands:
Cats can have significant impacts on
local wildlife populations, especially in habitat “islands” such as
suburban and urban parks, wildlife refuges, and other areas
surrounded by human development. The loss of bird species from
habitat islands is well documented, and nest predation is an
important cause of the decline of neotropical migrants. (Wilcove,
D.S. 1985. Nest predation in forest tracts and the decline of
migratory songbirds.
Ecology
66: 1211- 1214). The endangered Point
Arena mountain beaver, Stephen’s kangaroo rat, and Pacific pocket
mouse now live on habitat islands created by destruction and
fragmentation of their habitat in California. Predation by pet and
Photo: Lou Cohen
feral cats on these species is a serious threat to their future
existence. (Thelander, C.G. and M. Crabtree. 1994. Life on
the Edge. A Guide to California’s Endangered Natural
Resources: Wildlife. BioSystems Books, Santa Cruz,
California).
Cat Predation of Federally-Protected Wildlife
The Migratory Bird Treaty Act
(MBTA) prohibits the hunting,
taking, capturing, or killing of
any migratory bird. In seeming
violation of this landmark law,
owners of free-roaming cats
permit their pets to kill birds
protected by the MBTA. As
noted above, domestic cats are
also killing birds and other
wildlife protected under the
Endangered Species Act (ESA).
Through the ESA, the federal government protects and restores
wildlife at risk of extinction. Although cats may not be
responsible for the perilous status of endangered wildlife, the
loss of even a single animal can be a setback to the survival of
some species.
The Truth About Cats and Birds:
Well-fed Cats Do Kill Birds.
Well-fed cats kill birds and
other wildlife because the hunting instinct is independent of
the urge to eat. In one study, six cats were presented with a
live small rat while eating their preferred food. All six cats
stopped eating the food, killed the rat, and then resumed eating
the food. (Adamec, R.E. 1976. The interaction of hunger and
preying in the domestic cat (
Felis catus
): an adaptive hierarchy?
Behavioral Biology
18: 263-272).
Cats With Bells on Their Collars Do Kill Birds.
Studies
have shown that bells on collars are not effective in preventing
cats from killing birds or other wildlife. Birds do not necessarily
associate the sound of a bell with danger, and cats with bells
can learn to silently stalk their prey. Even if the bell on the
collar rings, it may ring too late, and bells offer no protection
for helpless nestlings and fledglings.
Most Birds That Seem to Escape Don’t Survive
Wildlife
rehabilitation centers report that most small animals injured
by cats die. Cats carry many types of bacteria and viruses in
their mouths, some of which can be transmitted to their
victims. Even if treatment is administered immediately, only
about 20% of these patients survive the ordeal. A victim that
looks perfectly healthy may die from internal hemorrhaging
or injury to vital organs.
Photo: David G. Smith
Cat with Blackpoll Warbler
Wedge-tailed Shearwater
For more information, contact:
AMERICAN BIRD CONSERVANCY
CATS INDOORS! THE CAMPAIGN FOR SAFER BIRDS AND CATS
1731 Connecticut Avenue, NW, 3rd Floor
Washington, DC 20009
Phone: 202/234-7181; Fax: 202/234-7182;
E-mail: abc@abcbirds.org; Web site:
www.abcbirds.org
A large percentage of patients at wildlife rehabilitation centers
are cat attack victims and animals orphaned by cats. At Wildlife
Rescue, Inc. in Palo Alto, California, approximately 25% of
their patients
between May and
June 1994 were
native cat-caught
birds, and almost
half were fledglings.
Thirty percent of
birds, and 20% of
mammals at the
Lindsay Wildlife Museum in California were caught by cats.
Cat predation of wildlife is especially frustrating to wildlife
rehabilitators. These losses are totally unnecessary because
Photo: Lindsay Wildlife Museum
unlike other predators, pet cats do not need to kill these animals
to survive.
Cat Colonies Are a Problem for Birds and Other Wildlife
:
Domestic cats are solitary animals, but groups often form around
an artificial feeding source, such as garbage dumps or food
specifically put out for them. These populations can grow very
quickly, can have significant impacts on wildlife populations, and
can cause significant health risks to other cats, wildlife, and humans.
Feeding these cats does not prevent the predation of birds and other
wildlife.
Conclusion
:
Cats are not ultimately responsible for killing our
native wildlife—people are. The only way to prevent domestic cat
predation on wildlife is for owners to keep their cats indoors!
Cat attacked Western Scrub-Jay