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You’re adamant. Your beloved Fluffy has never, would never, kill
a bird. Mice yes (but then who likes mice?), squirrels occasionally, and yes you have seen
her with baby rabbits. You’re sad about the rabbits of course, but then that’s nature, isn’t it?
Thank goodness she doesn’t kill birds, of that you are sure. Many cat owners in Wichita,
Kansas felt as you did until they took part in a year long study conducted out of Wichita State
University to determine what effect domestic cats are having on birds in Wichita. The results
may change your mind or at least make you wonder what Fluffy is really doing when
you’re not watching.
A group of 41 cats randomly distributed around the midwestern city of Wichita,
Kansas took part in a year long study from mid-May 1998 to June 1999. Their owners
gathered and bagged bird remains brought to them by their cat(s) and called a pager for
pickup. Fourteen of these owners also turned over fecal material, or scat, from their cat(s)
litter box. A total of 8 of the study cats (and a few strays) were tracked using radio
collars, and a random survey was used to determine cat density. There were many
questions the study hoped to answer. Do all cats kill birds? How many birds do
cats kill? Are some bird species more at risk? Does declawing influence
hunting ability? Do well-fed cats still take prey? Do cats bring prey to their owners? And, how many cats are there in Wichita anyway? If a problem
is found, how do people feel about regulating cats? Would they keep their cats
inside if it was found they are having an adverse effect on wildlife?
The results of the study were very conservative for many reasons. Only
actual physical bird remains were counted in the statistics. Many of the volunteers
reported seeing their cat kill and/or eat birds but were unable to collect remains.
Stories from volunteers, no matter how accurate or valid, were not counted as
kills. Several of the volunteers moved to other areas of the city, cats disappeared
for days on end (cat 6 was missing for two months), and some owners simply were
too busy to call with remains. Two of the owners thought the study was over when
there were several months left, and another owner threw out the instructions and
bags for the project. One owner put a bird in her freezer, but a relative threw it
out before she could turn it over to us. The list goes on and on, but despite the
many problems that are involved in using human volunteers to collect data, a total
of 113 birds representing 23 species were taken (a few bird remains were not
included in the total of 113). Identification of 17 of the remains was not possible
and may represent additional species. Many of the unknown remains were
taken from cat 18, the top predator, who brought partially eaten birds into the
owner’s residence, and these proved to be very difficult to identify. Cat 18, as
well as others, was declawed, and all but one of the 7 declawed cats caught
birds during the course of the study. Cat 18, a 3 year old neutered male, took
a total of 17 birds. It is likely that his kill record was actually higher as fecal
material was only obtained once for analysis of feathers during the study.
The greatest number of birds collected occurred during the months
of May and June, with secondary peaks in April and July. This is likely to be
a high risk time for birds in many cities throughout the U.S. as this is the time
when numerous birds are building nests and feeding young. However, the
majority of the birds taken were adults (69%) although it is likely that
many nestlings went undetected. The high requirements of feeding youngsters
may make the adults less vigilant, and the consequences to babies left alone
in the nest without a parent are most likely fatal. Several birds taken in the
study were alive when I went to retrieve them. Unfortunately, despite
constant care they all died. Cats carry many bacteria in their oral flora,
which are most likely deadly to birds, and it has been shown that most
birds who are cat caught, but later escape, die of injuries. Several of my
volunteers reported taking live birds away from their cats but insisted that
they were released and looked fine. Sadly, they probably were not; none
of these were counted in the statistics. Sixteen of the 27 owners reported
that they had seen their cat(s) climbing trees and/or getting into bird nests.
The majority of the bird species collected were those which have
adapted to humans. European Starlings and House Sparrows came in first
and second, respectively, in total kills; only one Rock Dove (common pigeon)
was collected. Together these three unprotected non-native species
comprised 27% of the total collected kills and are likely to be the
most populous bird species in many urban areas. The other 73%
represent an assortment of native birds, all protected under federal and
state laws, including an Eastern Screech Owl, a Yellow-billed Cuckoo,
a Lapland Longspur, and a Winter Wren. While no endangered or
threatened birds were taken, a Dickcissel was killed and partially
eaten by one of the study cats. This ground nesting grassland bird
has been identified as a bird of conservation concern. The protected
native bird taken in greatest numbers was the House Wren which
represented 9% of the total kills. While the House Wren population
as a whole does not appear to be at immediate risk, this research
suggests they are more likely to fall victim to a cat than perhaps other
birds. Ground feeding and ground nesting birds appear to be, in general
, at increased risk from cats.
In order to get a more complete picture of cat predation of
birds, owners were also asked to clean their litter boxes and call the
pager for collection. Many of the owners did not provide a litter
box for their cat(s) and some of the volunteers did not want to participate,
despite coupons from A&M Products for free Jonny Cat litter. It was
very difficult to solicit the help of volunteers for this part of the study
and one owner remarked that it was "too weird that you’re
collecting cat poop". However, collection and analysis of scat
revealed feathers in fecal material a total of 28 times. In 27 of the
analyses, the owners had absolutely no knowledge their cat(s) had
killed a bird. Not all cats eat the birds they kill, as evidenced by
many of the remains and observation of the cats, but when a cat does
ingest a bird, feathers in scat might revel this. Calculating
the percentage of time feathers are expected to be in scat when the
owner has no knowledge of a kill can be combined with average kills
from bird collection data to arrive at a better estimate for average bird
kills per cat. Unfortunately, nestlings, young juvenile birds, and well-plucked
birds would most likely not leave feather remains in scat. It is very
difficult to isolate wet feathers from hair and the process is lengthy
and causes a certain amount of eye strain. Almost every analysis
contained a fairly large amount of whole grass blades and during all
but the winter months, a considerable amount of invertebrate material
ranging from cockroaches and ants to crickets. Whole fleas were
found several times, and everything from pieces of plastic to shoelaces
and price tags were recovered. Every sample contained a large
amount of mammalian hair, most of which came from the cat itself.
Feathers were found numerous times in droppings from a cat
whose retired owner never failed to turn over scat on a monthly basis.
And yet this serious volunteer was not aware that her cat had
consumed a bird until she received the lab report, despite the
fact that she was often home with her cat. A total of 3 birds
were collected from this owner, but when scat analysis is included
it raises the number of kills to 17 which ties cat 13 with cat 18 for top
kill honors. It is likely that if all the owner volunteers had collected scat
the number of kills would be considerably higher; the owner of cat 13
was only one of 3 volunteers who collected scat every month for 5
consecutive days each month. The other 11 participants collected
scat only a few times, or just once, during the course of the study
for a total of 215 separate analyses. As a result of these findings, the
owner of cat 13 started to keep her cat inside at night before the
study concluded and later scat analysis revealed no feathers when
the cat was inside during hours of darkness. Once, the cat was known
to have stayed out at night and feathers were once again found.
Many of the study cats were seen taking birds during the hours of
daylight though, so confining cats solely at night does not guarantee
they will never kill birds. The data shows that 74% of cats out
at night catch birds, while only 50% of cats outside during daylight
hours kill birds. However, two of these daytime hunters took a
large number of birds.
Combination of scat data and bird kill data yields a value for
the average number of bird kills per urban house cat in Wichita per
year of 4.2, a very conservative estimate. Combining this with the
number of cats in Wichita gives an estimate of the number of birds
expected to meet their death due to a cat. However, determination
of cat density in an urban area is a daunting challenge. Some cities
require licensing of cats and this can at least give a rough estimate of
pet cats. Feral and stray numbers are much more difficult to determine.
Unfortunately, the city of Wichita has no laws governing cats except
a requirement for a yearly rabies vaccine, a poorly enforced law that
does not require veterinarians to report data.
Letters were mailed to veterinarians in and around Wichita
asking for the total number of rabies vaccines given to Wichita cats
in 1997. Several letters had to be sent and numerous phone calls
were made. The data proved to be extremely difficult to get despite
the promise of individual confidentiality, and quite surprisingly, a few
of the veterinarians were highly opposed to any study concerning
cat predation, so data from 7 offices had to be estimated from the
mean of the other 54 veterinarians. Since this provided only information
concerning vaccinated pet cats, a random survey was conducted to
obtain the rest of the data.
Dr. Ellie Shore, a psychologist at Wichita State University,
wrote a telephone survey of people and their pets, and
included in this Pet Ownership Survey
were questions for this study which asked residents how many strays
they see or feed, whether their cat(s) was vaccinated, and how they
felt about cat predation, as well as questions concerning regulation
of cats. The data indicated that just under 88% of cat owners
claimed their cat(s) had a current rabies vaccine, a highly questionable
value that may suggest participants were less than truthful. Information
about feral and stray cats from the telephone survey was not asked
of people who did not own at least one cat or dog, and it is likely
that non-cat/non-dog residents may have seen more strays. This
would yield a low estimate for feral cats.
The long-term ecological implications of cat predation on birds
in Wichita are far from clear. More investigation is called for, especially
with regards to such sensitive birds as the Dickcissel. Certainly there are
many threats to birds besides cat predation; habitat loss on wintering
and nesting grounds may be the primary factor in the decline of many
songbirds. Cats may not be one of the primary causes of avian
mortality, but they do kill birds, and in some areas may well prove
to be a cause for serious concern. The latest estimate of the number
of pet cats in the U.S. is from the 1999-2000 American Pet Products
Manufacturers Association’s Pet Owner Survey which estimates there
are 64 million pet cats in the U.S. It seems reasonable to assume that
on the basis of the pet cat population alone in this country, that if each
cat killed 4.2 birds per year as did the average cat in this study, this
would result in the death of at least 269 million birds per year due to
predation by pet cats alone. Further assuming that half of these cats
never go outside (e.g., the phone survey in this study indicated that
43% of pet cats were never allowed outdoors), at least 134
million birds could be expected to die as a result of domestic pet cats.
It is likely that well under 43% of pet cats are kept strictly inside,
especially if rural cats are considered. The inclusion of feral and stray
cats would greatly increase this figure.
If any of us were caught killing or injuring even one of these
birds, we might face federal prosecution which could include fines
and possible jail time. And yet cats across America face no punishment
(scolding your cat doesn’t count). In fact the law is so strict that
I had to obtain federal and state permits just to pick up the dead
birds, and detailed yearly reports must be filed. Collection of birds
and remains, feathers, eggs and nests are all against the law unless
the necessary permit(s) are obtained.
Radio tracking of cats in this study indicate that frequently
owners have inaccurate, if any, information about the whereabouts
of their cat. Cats were often wandering after dark when owners
claimed they were kept in at night. Some cats had large ranges
and all had well concealed hiding places. Tracking cats was very
difficult, and despite a resident’s perception of numbers of wandering
cats in their neighborhood, roaming cats were observed in virtually
every yard during tracking. Cats were seen to easily climb and
descend trees, stalk rodents, invertebrates, and birds, and to scale
with ease, solid 8 foot high privacy fences. Cats were also seen
leaping from various structures and easily climbing onto roofs and
into vehicles such as trucks and boats. Frequently cats were
observed on roadways.
The telephone survey also asked residents how they felt
about regulating cats, and quite surprisingly 44% of cat owners
said they would be at least somewhat in favor of a leash law for cats.
An even higher percentage of dog owners were in favor. When cat
and/or dog owners were asked "If it were found that unregulated
cats are killing too much wildlife, would that change your opinion?",
32% of all the people who had originally been opposed to
regulation (or had no opinion) said "Yes". A leash law would require
owners to keep their cat(s) confined to the property at all times, a
difficult law to enforce. A nuisance law is an alternative to a leash
law and would allow residents who did not want roaming cats on
their property to humanly remove them and have them transported
to the shelter. During the course of this study I heard more
than a few inhumane methods for disposing of unwanted cats. A
nuisance law could help eliminate some of these cruel, and perhaps
illegal, acts by desperate people.
All cats hunt. Although the cats in this study were well-fed
(and neutered), actual physical bird remains were collected from
83% of them. This suggests that hunger and hunting are
independent. Feeding your cat will not eliminate the
instinct to hunt. Males (91%) and females (72%) both hunted
birds, and declawing had absolutely no effect on hunting ability. Many
other studies have shown that using bells on collars is also ineffective,
and tracking from this study has shown that fences are totally useless
barriers to cats. The only way to protect birds from cats is to keep
cats inside. Cat owner education (such as the American Bird
Conservancy’s "Cats, Indoors!" project) supported by local
veterinarians and actively publicized by city officials, can go a long
way in protecting our native birds, many of which are in serious trouble.
Keeping cats indoors, at least at night, during the high risk
months is my minimum recommendation. Confining cats
indoors year round is the best solution and one that is much better
for the cat too. Indoor cats lead a longer healthier life and are less
prone to many diseases and parasites (this will most likely result in
less bills for you). Unfortunately, one of the cats that was tracked
was hit and killed by a car before the study was completed; cats
do face real dangers.
Remember two important points; firstly, it is against the law
to injure birds, and secondly, don’t shrug your shoulders and say
"...but that’s what cats do. It’s a normal part of life." Cats are
introduced predators. They are not a natural
part of the ecosystem of North America and our native wildlife did
not evolve in the face of this accomplished predator. When
native wildlife preys on birds, that is part of
the "circle of life". Cats do not face the population controls that
other species do and their current numbers are staggering and continuing to grow.
Picture this. A small bird sits on her nest. She has built her
home close to the ground, as many of our native birds do. Her
babies are just a few hours old. It is dark, and although she sits
very still, a cat (maybe yours?) has spotted her. The cat moves
silently towards her. He is declawed and wears a small bell on
his collar. It doesn’t matter. The tiny bird and her babies don’t
have a chance.