Alarming number of fledgling, suburban catbirds fall prey to domestic cats, study finds

Gray catbird–Dumatella carolinensis (Photos by Johnny N. Dell, Bugwood.org)

There comes a time in life for every bird to spread its wings and leave the nest, but for gray catbirds, that might be the beginning of the end. Smithsonian scientists report fledgling catbirds in suburban habitats are at their most vulnerable stage of life, with almost 80 percent killed by predators before they reach adulthood. Almost half of the deaths were connected to domestic cats.

Urban areas cover more than 100 million acres within the continental the United States and are spreading, with an increase of 48 percent from 1982 to 2003. Although urbanization affects wildlife, ecologists know relatively little about its effect on the productivity and survival of breeding birds. To learn more, a team of scientists at the Smithsonian’s Migratory Bird Center studied the gray catbird (Dumatella carolinensis) in three suburban Maryland areas outside of Washington, D.C.—Bethesda, Opal Daniels and Spring Park.

A domestic cat–Felis catus (Photo by Terry Spivey, USDA Forest Service, Bugwood.org)

The team found that factors such as brood size, sex or hatching date played no significant role in a fledgling’s survival. The main determining factor was predation, which accounted for 79 percent of juvenile catbird deaths within the team’s three suburban study sites. Nearly half (47 percent) of the deaths were attributed to domestic cats in Opal Daniels and Spring Park. The deaths were either witnessed by the scientists or determined to be cat-related by the condition of the fledgling’s remains, such as a decapitated bird with the body left uneaten—defining characters of a cat kill. Domestic cats were never detected during predator surveys in the third suburban study site, Bethesda.

“The predation by cats on fledgling catbirds made these suburban areas ecological traps for nesting birds,” said Peter Marra, Smithsonian research scientist. “The habitats looked suitable for breeding birds with lots of shrubs for nesting and areas for feeding, but the presence of cats, a relatively recent phenomenon, isn’t a cue birds use when deciding where to nest.”

Gray catbird–Dumatella carolinensis (Photos by Johnny N. Dell, Bugwood.org)

Technology made tracking the fledgling catbirds possible. The team fitted 69 fledglings with small radio-transmitters. Scientists tracked each individual and recorded its location every other day until they died or left the study area. This detailed type of field research was very limited until recently when transmitters were made small and light enough for songbirds.

Tracking the fledglings revealed that the vast majority of young catbird deaths occurred in the first week after a bird fledged from the nest. This was not surprising to the team, given that fledglings beg loudly for food and are not yet alert to predators—making fledglings in suburban environments particularly prone to vis

ual predators such as domestic cats. Domestic cats in suburban areas that are allowed outside spend the majority of time in their own or adjacent yards, so they are likely able to intensely monitor, locate and hunt inexperienced juvenile birds. Rats and crows were also found to be significant suburban threats to fledgling catbirds.

“Cats are natural predators of not just birds but also mammals—killing is what they are meant to do and it’s not their fault,” said Marra. “Removing both pet and feral cats from outdoor environments is a simple solution to a major problem impacting our native wildlife.”

The scientists’ findings were published in the Journal of Ornithology, January 2011 –Johnny Gibbons

 

 

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  • Adrian Cherry

    I was under the impression that similar studies in the UK had determined that cats had no major impact on bird numbers unlike climate and environmental factors.

  • Doug Hayden

    We moved into our house five years ago,we had birds,every where,-one cat,behind us.Now six cats around us.NO birds! WE do have some crows,but we had them before. Your study confirms what has gone on in my back yard…

  • http://www.voxfelina.com Peter J. Wolf

    This story is as full of holes as it was last October when the Smithsonian’s Migratory Bird Center tried to sell it to the public. In short, it looks as if the people responsible are far more interested in making scapegoats out of the cats than they are in any rigorous scientific inquiry.

    Let’s start with that 47 percent figure. It doesn’t correspond at all with what’s reported in “Population demography of Gray Catbirds in the suburban matrix: Sources, sinks and domestic cats,” upon which this article is ostensibly based.

    According to authors Anne L. Balogh, Thomas B. Ryder, and Peter P. Marra (all of whom are affiliated with the Migratory Bird Center), the Opal Daniels and Spring Park sites accounted for 34 of 42 total juvenile mortalities. The presumption, then, is that 16 (47 percent) are due to cats. However, cats accounted for—at most—just nine of the 42 total mortalities (no breakdown regarding kills/site is provided in the paper).

    Something doesn’t add up here—and I suspect it’s no accident.

    But attributing even nine kills to cats is highly questionable. Only six were actually observed. The researchers then attributed three additional kills to cats, claiming: “we are unaware of any other native or non-native predator that regularly decapitates birds while leaving the body uneaten.” In fact, it’s rather widely known that such predatory behavior is not uncommon with owls, grackles, jays, magpies, and even raccoons.

    The authors also point out that another “potential nest predator,” the gray squirrel, was more common at the Opal Daniels and Spring Park sites than at the Bethesda site. And roughly three to five times as abundant as cats, based on researcher sightings. Yet the squirrels aren’t mentioned here at all.

    Marra’s suggestion that “these suburban areas [are] ecological traps for nesting birds” raises additional questions. According to the North American Breeding Bird Survey, Maryland’s gray catbird population has increased about 9 percent between 1966–2009, a period during which the state’s human population grew approximately 59 percent. And data from BBS Route 46110, the nearest to the research sites, also trend upward in recent years. (Note: It’s important to point out that “the survey produces an index of relative abundance rather than a complete count of breeding bird populations.”)

    The Migratory Bird Center’s Website, too, suggests the outlook for the catbird population is quite good:

    “To thrive in these [fragmented] habitats birds must have special adaptations such as the ability to respond to frequent nest predation and parasitism and to forage on a wide variety of seasonally available foods. Armed with these adaptations, catbirds are well prepared for the disturbed habitats of the 21st century’s fragmented landscape.”

    Marra revealed his position on free-roaming cats last year when he co-authored a letter to Conservation Biology opposing Trap-Neuter-Return, a humane approach to feral cat management. Among the “highlights” were the authors’ assertion that “trap-neuter-return is essentially cat hoarding without walls,” and a demand for “legal action against colonies and colony managers.” The authors also call on conservation biologists to “begin speaking out” against TNR “at local meetings, through the news media, and at outreach events” (a message Marra has obviously taken to heart).

    According to its Website, the Smithsonian Migratory Bird Center is a “national and international leader in the biology and conservation of migratory birds.” In this case, though, it seems the Smithsonian has abdicated its leadership role in order to participate in the shameful witch hunt against free-roaming cats. Your supporters—and the public at large—expect and deserve better.

    Peter J. Wolf
    http://www.voxfelina.com

  • T.L. Scott

    I have a problem with the following points in your article

    {Quote}The deaths were either witnessed by the scientists or determined to be cat-related by the condition of the fledgling’s remains, such as a decapitated bird with the body left uneaten—defining characters of a cat kill. {End Quote}

    I feel like some one is selling me ocean front property in Arizona

    Actually the define characteristics of a bird killed by a cat is scattered feathers, and feline paw prints otherwise for all you know the bird could have been hit by a truck.

    {Quote}Urban areas cover more than 100 million acres within the continental the United States and are spreading, with an increase of 48 percent from 1982 to 2003. Although urbanization affects wildlife, ecologists know relatively little about its effect on the productivity and survival of breeding birds. {End Quote}

    If any thing else urbanization probably increases the cat population by a little along with huge increases n pollution, traffic, buildings, boys with bee bee guns, pesticides, Urbanization also has the nasty side effect of decreasing natural resources for all species of wild life including birds. I don’t need to be a forgetful ecologist to figure that one out.

    {Quote}Rats and crows were also found to be significant suburban threats to fledgling catbirds. {End Quote}

    Yet they were not even mentioned in your head lines – why?

    The title of the article is noting more than feckless allegation.

    {Quote}“Cats are natural predators of not just birds but also mammals—killing is what they are meant to do and it’s not their fault,” said Marra. “Removing both pet and feral cats from outdoor environments is a simple solution to a major problem impacting our native wildlife.” {End Quote}

    As a “scientific” publication you could not possibly have considered that some of the other “natural prey” of free roaming cats are crows and rats !!!!

    According to my elementary science education eliminating free roaming cats from the environment will most likely lead to an increase in rat, crow, snake and squire populations therefore the catbirds mortality rate at best would remain at the same level but mostly likely it would actually decline!

    Your malevolence for domestic cats if painfully obvious. Your “simple solution” is despicable, rendering your article nothing more than distorted propaganda,

    I have just lost all respect for the Smithsonian as a scientific institution.

  • Steve

    I have figured out why cat people are so fanatical about it. Toxoplasma gondii. This is the parasite spread via cat feces. The oocysts embed in the host’s brain and the species can only reproduce if it makes it into another cat. In a clinical study, the presence of oocysts in rat brains led them to lose their natural fear of cats/cat urine. If you think about it evolutionarily, the parasite (over millions of years) figured out where to go in the brain to alter the behavior of the host to put it someplace where it would be eaten by a cat. In modern times, this parasite is causing people to hoard cats, feed cats, defend TNR, or like Mr. Wolf to spend inordinate amounts of times on the internet, spewing pseudo science in the hopes that this will result in more cats outdoors.

    • http://www.voxfelina.com Peter J. Wolf

      In addition to your comment being, at best, unhelpful, I’m curious about your suggestion that I’m “spewing pseudoscience.”

      Perhaps you might do us all the courtesy of being as specific as I’ve been (requiring, as you say, “inordinate amounts of times”). Are you referring to my quoting the very paper upon which this story is allegedly based?

      Or the reports–including one by Marra’s colleague–about decapitated birds being the work primarily of other birds?

      Or perhaps it’s the BBS data indicating that the area’s catbird population is actually on the rise?

      I go out of my way to be support my claims with ample documentation, to be transparent, and so forth. Is it really too much to ask that others do the same? Or, failing that, at least have the courage to identify themselves?

      Peter J. Wolf
      http://www.voxfelina.com

    • Jeremy Williams

      @Steve,

      So when you can’t refute Peter’s post with facts, (or even weak opinions) you resort to making a toxoplasmosis joke based insult.

  • GW

    Thanks for this great article! I have a cat lady on my block and there seem to be more cats and fewer birds all the time — this explains why! Cats need to stay INSIDE, away from wildlife that has no other home!

  • Anna

    There is no way in the world anyone can possibly claim to have witnessed every bird death and attributed it to cats! Maybe in one park, but that’s hardly the whole country! Cats have been running around for hundreds of years and there was no bird shortage until recently. Get a clue- the REAL reason for songbird depletion is the average suburbanite’s quest for a perfect green lawn, and a farmer’s desire for a higher volume crop. It’s the CHEMICALS that are killing the birds by poisoning the bugs and worms they use for food! Another huge factor is deforestation. Where are all the bird lovers when nests fall with trees being cleared out for the newest, unnecessary strip mall or subdivision? The biggest proof it’s HUMANS and their CHEMICALS and not cats is that HONEYBEES are also disappearing, and cats don’t eat them!

    • Jim Greaves

      yup, I agree. chemicals caused the decapitations

  • Steve

    It’s really pretty simple folks. North American birds did not evolve with a small somewhat arboreal predator like cats. Therefore they have not evolved the characteristics needed to deal with this predation. It will always be ‘unnatural’. Did you know that cat saliva contains a bacteria lethal to birds? They could escape a near miss and still die later on, never discovered by cat owners or the Wisconsin study Mr. Wolf.

    Cats kill birds. Cats are non-native to North America. PETA believes TNR is inhumane. Cats harbor parasites and diseases harmful to humans. Why do we have a group (Alley Cat Allies) advocating their continued persistence in an environment hostile to them. Do I need to post pictures of cats killed by cars, cats ripped about by dogs and coyotes? Humane euthanasia is preferable to a life on the street and 100% more humane for the wildlife these street cats will kill or maul REGARDLESS of the numbers.

    • Maria

      Because… we need Alley Cat Allies to dispute the uninformed like you. Feral cats are happy and healthy living outdoors with good caretakers. You clearly have never experienced a feral cat. Who do you think you are to decide that a cat would be better off dead? I’ve seen and helped thousands of feral cats. And I can tell you, they are happy and healthy. And they love going home, back outside, where they belong!

      PETA has definitely jumped the shark. What kind of animal protection agency advocates mass killings??? UNBELIEVABLE.

      http://www.alleycat.org/NetCommunity/Page.aspx?pid=897

  • Steve

    Peter,

    Were is the reference for decapitated birds NOT being a characteristic of a cat kill?

    Here’s Gray Catbird trends in Chicago
    http://bcnbirds.org/trends07/GRCA.htm
    (another city with growing street cat problems)

    BTW, you should never used a single BBS route to determine trends in bird species decline.

    BUT, hey, let’s put this back in your world. You folks don’t want a single cat euthanized because you value individual cat life. Why can’t I believe the same for birds. I value every bird life killed by UNNATURAL means – predators, collisions, habitat destruction, etc. I want to minimize all such loss. One way to do so with collisions is to put up UV decals, one way to do so with cats is remove them from the environment through education or trapping. It’s all good, and more individual lives will be saved by the removal of one cat. Ciao baby.

    • http://www.voxfelina.com Peter J. Wolf

      Two references to the decapitated birds were included in my original post on the subject (http://www.voxfelina.com/2010/10/a-tale-of-two-cities/).

      An additional reference–along with statewide BBS data–is included in my follow-up post (http://www.voxfelina.com/2011/03/catbirds-cats-and-scapegoats/).

      By the way, I’m not buying the non-native/non-natural argument. Let’s say scientists make an amazing discovery–that domestic cats had been in North America for many THOUSANDS of years. Does that change your view of things? Does predation by cats suddenly belong in another column of your accounting ledger? I rather doubt it.

  • Maria Foster

    @Steve,

    {Quote}Do I need to post pictures of cats killed by cars, cats ripped about by dogs and coyotes? Humane euthanasia is preferable to a life on the street and 100% more humane for the wildlife these street cats will kill or maul REGARDLESS of the numbers.{/quote}

    According to your logic, we should then “humanely” kill all outdoor animals. Foxes, squirrels, deer, racoons and, yes, even birds, all get hit by cars, mauled by other animals, sick from pesticides, driven from their homes by builders, etc. Should we just kill all of them now so that they won’t be exposed to a horrible death later on?

    People get hit by cars, shot, stabbed, etc. Should we just kill them all now so that they can avoid the possibility of a horrible death later on?

    None of these animals deserve any more or any less of a right to life. Killing one animal because it might kill another animal is still killing an animal.

    I personally would prefer that pet cats are kept indoors. However, feral cats are not pets…their home IS outdoors.

    I am always bothered by people who seem to suggest that the protection of one animal must come at the expense of another animal. There are much more humane, tried, and tested options to killing. TNR being one of them.

  • Cait

    Steve:

    You really should familiarize yourself with PETA before you go claiming to speak on their behalf. PETA does not support mere TNR by itself–they support TNR with colony maintenance. Their point is that it is not good enough to merely TNR feral cats; they also need to be managed so they get adequate access to food, shelter, and health care.

    PETA is an animal rights group; their point about TNR is its relation to the cats THEMSELVES, not how feral cats affect BIRDS. Your comment is not directly related to this argument.

    To add to this discussion, your point that “humane euthanasia is preferable to a life on the street” is speciesist and inaccurate. Obviously Alley Cat Allies does NOT support letting cats run wild and live unsafely. Like PETA, they support TNR in addition to maintaining cat colonies for their safety and health. If you think that it’s better to euthanize cats than let them live on the street, then why not do the same to dogs? Birds? How about humans? It is considered unethical to “euthanize” a human, but we let them live on the street, and many homeless people have mental and physical health problems. We advocate putting them in shelters or giving them help, not euthanasia. Are cats so different? In your mind, they must be, but many people do not agree.

  • Steve

    Peter,

    In your hypothetical scenario, birds would have evolved with the cats and would have developed the mechanisms necessary to deal with predation. If they had become extirpated before the arrival of man I would not support bringing them back. If they had held on in small pockets, they would be an endangered species (ocelots for example) and I would all for their recovery. It is not predation on birds that’s the problem. It’s the fact that they are NON-NATIVE!!! Yes, humans are also, but that is a WHOLLY different situation and and comparison is specious at best.

    Cait,
    1. From a pro-TNR website:
    “PETA is the last major animal advocacy group in the U.S. that overtly opposes TNR feral cat control and no-kill sheltering.”
    From PETA’s website:
    http://www.peta.org/issues/companion-animals/outdoor-cats.aspx
    and:
    “Nevertheless, PETA’s position has never been that all feral cats should be euthanized. We believe that trap, vaccinate, spay/neuter, and release programs are acceptable when the cats are isolated from roads, people, and other animals who could harm them; regularly attended to by people who not only feed them but care for their medical needs; and situated in an area where they do not have access to wildlife and where the weather is temperate”
    2. We do capture and euthanize stray dogs. No one has yet advocated TNR for dogs. Why? Because society doesn’t accept it. Dogs can kill humans. My goal is to show that cats, when allowed outdoors and free-roaming are detrimental to both humans and wildlife.

    I support TNR where the colonies are in large outdoor enclosures on private property and the cats do not stray off said property.

    Maria,

    Native wildlife is just that. WILD life. Natural prey-predator relationships are at work. Feral cats are supplementally fed 365 / year and as such normal predator-prey interaction just doesn’t take place. They (cats) exist in densities that can be locally disastrous to wildlife populations.
    (TNR has NOT been proven to reduce POPULATIONS of cats. It can only work on the colony level and works mainly by the removal of kittens and adoptable adults. NOTE: REMOVAL!! Even then it can not, and has not reduced populations to zero so it is NOT a solution for municipalities. What is ORCAT up to now? $60,000 – $100,000 / year and still can’t get below 300 cats? Doesn’t sound like a solution to a problem to me.

    • Debbie Watroba

      On the contrary, TNR does work. If all the cats that were trapped, neutered and returned were left alone, they would reproduce over and over again, creating larger and larger populations of feral cats. TNR cats do not reproduce and their numbers diminish gradually as a result through natural means. If you kill all the cats in an area, more will just move in and take over the abandoned territory because humans will not neuter their pets and keep them indoors. There will always be feral cats as long as humans are irresponsible pet owners. All feral cats descend originally from pets that were abandoned or lost. TNR DOES WORK.

  • Steve

    Peter,

    The article was published in the Journal of Ornithology. REAL scientists, if they disagree, publish a rebuttal, which is also peer removed. Pseudo-scientists fill up a web-page which anyone can do. Which are you again?

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  • Christina

    The only thing I have to say is that we have tons of stray cats in my neighborhood and thousands of birds in our yards. But we live in a town, not a city and not a crowded town. I can’t get all scientific like some but I have observed that there seem to be fewer birds in cities and crowded towns, while on the outskirts of the towns there are thousands of birds. Perhaps this is because cities and towns require more buildings and less trees, where birds have to nest. Yes, birds can nest on buildings and I have seen birds at schools nesting under the coverings. But I have also seen humans destroy their nests and throw rocks at them simply because they think it’s funny. Humans are a problem to the whole world, I don’t care who says what about it. Humans cause animals to go extinct, not animals. Humans over hunt, over fish, kill for sport, kill for pleasure, and many other terrible actions that cause everything to suffer, animals and plants alike. So before people go all “the Smithsonian proved this and that” include people before anything else because the growing human population is the number one problem of everything. I am a cat lover but I’m also concerned about the rest of the animals that others may have forgotten or just disregard. As people who care about wildlife, whether it be birds or cats or whatever, we have to face the fact that humans are the biggest threat to wildlife. If you believe otherwise then you’re blind to your world.

  • Steve

    Christina,

    Isn’t allowing cats to roam free or re-releasing trapped cats back into the environment human caused?

    I guess I have to agree with you then. I’ll choose to protect and create habitat, minimize collisions with my windows AND control cats in my yard and neighborhood in order to minimize the negative effects us humans cause to bird life.

  • Debbie Watroba

    For heavens’s sake, just keep your cats indoors to prevent the problems of them killing birds. AND to prevent them from getting lost and reverting to feral, or getting killed themselves by cars and all the many predators out there. Humans are totally responsible for this problem and are trying to foist the blame onto the cats. They are innocent. Neuter your pets. Keep them indoors. I am so appalled by the ignorance and stupidity regarding this issue.

  • Barbara

    As a longer term resident of Westchester County and witnessing over 15 years the desolation of a woodland, I can state what has happened HERE and is was not the cat.

    We had many many thousands of birds in THIS area and it wasnt that many years ago. The one important change was the arrival of predator birds. And they arrived in many pairs and it took maybe 10 years to lose everything.

    Wintering birds were crushed,. They did not survive, squirrels and chipmunks were obliterated becoming food for more and more predator birds. Orioles were nesting here and we had scores of them, But as a daily visitor in this woodland almost 30 years I saw what happened to them. Bright and flashy and consipicuous just as the woodpecker, I saw hawks just swallow them in the trees where they nest. I saw one tiny woodpecker a month ago, just for an instant, you could have missed it, and in a flash that tiny bird was taken out by a hawk.

    With just a few squirrels remaining, I saw only ONE in this woodland, wwe had many many hundreds 15 years ago! and my small dog actually found it, a baby maybe a couple months old, and it was dead with an organ bloodied, and I looked up and there in a tree was a juvenile redtail, and that creature didnt even eat that baby, it just played with it.

    Making matters infinitely worse for ALL our beautiful things, was the death of the crow.
    This was a disaster of major proportions………Millions of them, gone.

    They were the only life preservers for lesser birds………….but the reason for THEIR DEMISE the west nile came from where? maybe some flamingoes brought in from some prominent zoo?? improperly quarantined???

    What has happened here, with redtails and perigrines killing to produce more killer birds WILL hit areas surrounding, it takes a few years…. Ten for this area.

    Wintertime next year should see really dramatic reductions in every bird north of NYC (aside from english sparrow, starlings, and the canada goose) Bird feeders attract redtails. red shouldered, and the whole family of exterminators, imagine how many chicadees are swallowed at feeders!!! And I have first hand experience with this.

    My granddaughter, not 8 years old and I OUTSIDE at her peachtree feeder saw a swooping large bird pass a small grouping of chicadees flying to her feeder! THIS HAPPENED 7 YEARS AGO…Within an instant those chicadees were swallowed! Now my granddaughter refused to compromise what she loved, but how many birds are killed at feeders? How many people use FEEDERS???

    Just as uncaring people from various bird societies placed predator birds in cities around the USA decades ago, what they encouraged will spread to areas not yet severely impacted. They can never admit what their intervention set in place, the devastion of all lesser species. From the patio rail to the window in my home the past year the most enormous redtail whose shadow and shrieks have finally come to an end but this is due to the extinctions of every bird sound here, this dreadful desolate spring, the perigrines, the redshouldered have moved north. And I have seen not even one squirrel.

    These past years 10-15 brought back predators nationwide through human intervention in a big way and they have returned dramatically with consequences far reaching from the desolation in the parklands (only in this area?) to the losses of species in grasslands and shore.

    We lost everything WESTCHESTER COUNTY.

  • Pamela Check

    Why are their hungry and feral cats in the first place? Irresponsible human beings. It isn’t just the people who don’t spay and neuter; there are the elderly and sick who have animals and, in an emergency or death, the first people in open the door and leave it open and don’t give a damn about the cats who flee in terror. Why are the victims blamed? Because people don’t want to take responsibility.

  • Jeff

    Catbirds are particularly naive and vulnerable. I’ve had a young one eat from my hand and adult catbirds happily sit next to me eating peanuts. Some have even mimicked my whistles, over and over again, right on pitch. They are sweet birds with a variety of melismatic songs, beyond its mewing calls.

    We have four half-domesticated cats living outdoors. One cat in particular has a predilection for songbirds and the species I find killed more than not is the Gray Catbird. So I can personally attest to this article. This cat has also climbed kolkwitzia bushes in an attempt to raid nests. I happen to be outside a lot and have prevented a few of these attacks. Let’s just say that when this cat sees me it takes off real quick!
    I’ve also encountered Blue Jays raiding a Catbird nest which I foiled as well.

    Upon researching preventative measures for saving songbirds from cat predation, I did find two possibilities which I have yet to try: the CatBib and the Bird Alert Cat Collar.