So, You Say Your Cat Doesnít Kill Birds...

Carol Fiore
Wichita State University, Kansas


Youíre 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. Youíre sad about the rabbits of course, but then thatís nature, isnít it? Thank goodness she doesnít 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 youíre 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 ownerís 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 youíre 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 Associationís 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 doesnít 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 residentís 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 Conservancyís "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, donít shrug your shoulders and say "...but thatís what cats do. Itís 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 doesnít matter. The tiny bird and her babies donít have a chance.


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