A Tale of Two Cities

Gray Catbird (Dumetella carolinensis)A Gray Catbird in Madison, Wisconsin, USA. Photo courtesy Wikimedia Commons and John Benson.

According to its website, the Smithsonian Migratory Bird Center is a “national and international leader in the biology and conservation of migratory birds.” When it comes to cats and their potential impact on birds, however, the SMBC apparently has a lot to learn.

Actually, they could use some pointers on professionalism, too—and maybe a refresher on the difference between correlation and causation.

Summarizing a recent study of gray catbird fledglings in the Washington, DC area, the SMBC claims that cats were responsible for “alarmingly high rates of nest predation and fledging [sic] mortality.” But there’s no mention of how such a connection was made. Indeed, “Baby Catbird Survival” offers very little in the way of details. Instead, readers are treated to sophomoric commentary:

“… several guilty-looking cats were found in close proximity to dead birds. Our guess is that closer examination would have revealed feathers in their whiskers.”

This is the Smithsonian? What I wouldn’t give to have been in the marketing meeting where “predation humor” was first proposed as an innovative, sure-fire scheme for attracting new donors and research funding.

Catbird Mortality
The study, spanning two summers, was conducted at three sites, two in Takoma Park, MD, and another—apparently less populated with cats—in Bethesda, MD. Somehow—again, no details are given—radio-tracking technology was used to monitor the mortality of young catbirds.

Results indicate that 85% of nests at the Bethesda site were “successful” (i.e., young catbirds survived long enough to leave the nest), compared to only 34% of nests at the Takoma Park sites. At the Bethesda site, 29% of fledglings survived to eight weeks of age, versus 14% at Takoma Park.

Given the rather dramatic nature of these findings, one might expect some explanation of the research methods and analysis techniques employed. Among the numerous questions left unanswered:

  • How was radio-tracking used to distinguish predation from other forms of mortality—or, more to the point, predation by cats from other forms of predation?
  • How were the sites selected, and the cats at each site counted?
  • What other factors (e.g., population density of humans, abundance of other predators, habitat availability and condition, etc.) might have been at work here?
  • What were the sample sizes employed?

At best—and this is being very generous—the results suggest correlation. But, of course, this is very different from causation.

In Proofiness, author Charles Seife uses the relationship between a country’s energy consumption and the life expectancy of its citizens to illustrate the difference. Plot the data and there is an unmistakable trend: as energy consumption increases, so does life expectancy.

“Yes, it’s true that the more power a society uses, the longer its citizens live, on average. It’s equally true, however, that the more garbage a society produces, the longer its people live. The more automobiles people in a society drive, the more newspapers people in a society read, the more fast food people consume, the more television sets people have, the more time people spend on the Internet…” [1]

So, are the Takoma Park cats the cause of catbird mortality? Who knows.

Who’s In Charge?
Exactly who’s responsible for “Baby Catbird Survival” is another mystery (though anonymity is understandable in this case, as it’s difficult to imagine any respectable scientist claiming ownership of something so flimsy and irresponsible). The researcher who oversaw the project, though, is Peter Marra, the SMBC scientist at the center of a recent Washington Post column (of which I was highly critical).

This, of course, is the same Peter Marra who, along with nine of his colleagues, has argued that “trap-neuter-return is essentially cat hoarding without walls,” and called for “legal action against colonies and colony managers.” [2] The authors also call on conservation biologists to “begin speaking out” against TNR “at local meetings, through the news media, and at outreach events.” [2] It’s a message Marra has obviously taken to heart.

There’s no doubt Marra has an agenda. The question is: how might this bias his research?

Untangling the Research
With so few details to go by, it’s difficult to scrutinize Marra’s catbird study. If it’s published, of course, greater transparency will be required. In the meantime, we do have some useful clues that—along with a little detective work—provide some insight.

Counting Cats
As I indicated previously, it’s hard to imagine that the only difference between the Takoma Park and Bethesda sites was the number of cats. Even if that were the case, though, absolute numbers are hardly the whole story. Numerous studies have demonstrated that predation success varies widely among domestic cats: some catch lots of prey while others catch very few—or none at all. [3–7]

That’s assuming they can get at the prey, of course.

Marra is clear in the Post piece that the (alleged) killers “aren’t feral cats; they’re domestic cats allowed to go outside.” But, contrary to what columnist Adrian Higgins suggests, studies have shown that about two-thirds of cats are indoor-only. [8–11] And of those allowed outside, approximately half spend less than three hours outdoors each day. [9, 10]

How sure can Marra be, then, that the areas’ pet cats are responsible for the deaths of young catbirds?

Predatory Habits
The author of “Baby Catbird Survival” claims that “domestic cats typically only decapitate birds and leave the carcass.” Now, I’ve become quite familiar with the research on the hunting behavior of cats over the past year or so, and recall seeing nothing to this effect. I recently revisited some key sources [12–15] just to be sure, and again found nothing to support this assertion. However, it was brought to my attention that some birds will decapitate their prey:

“In urban and suburban settings grackles are the most likely culprits, although jays, magpies, and crows will decapitate small birds, too. Screech-owls and pygmy-owls also decapitate their prey, but, intending to eat them later, they usually cache their victims out of sight.” [16]

“There is little you can do to discourage screech-owls if only because they do their killing under cover of darkness. However, you can recognize their handiwork by looking for partially plucked carcasses of songbirds with the heads missing… Corvids—crows, ravens, jays, and magpies—are well known for their raids on birds’ nests to take eggs and nestlings.” [17] (Interestingly, the author, David M. Bird, was among Marra’s nine co-authors on “What Conservation Biologists Can Do.”)

Again, how can Marra be so sure the cats are the culprits?

Catbird Population
And finally, what about Marra’s claim, as reported by Higgins, that “catbirds in cat-heavy areas are not able to reproduce at a rate that is sustainable”?

Data from the North American Breeding Bird Survey suggest that Maryland’s gray catbird population declined perhaps 7% between 1966–1989, a period during which the state’s human population grew approximately 35%.

BBS Data: Catbirds Across MarylandBBS Data: Gray Catbirds Across Maryland (adapted from the Atlas of the breeding birds of Maryland and the District of Columbia)

Even so, the Atlas of the Breeding Birds of Maryland and the District of Columbia—which includes the aforementioned BBS data in its assessment—reports that, “during the Atlas period [1983–87], gray catbirds were found throughout the state, including the most heavily urbanized blocks.” The Atlas goes on to note the bird’s “high tolerance for human activity,” concluding that “the gray catbird’s future in Maryland seems secure.” [18]

Indeed, the SMBC itself echoes the Atlas’ assurances:

“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.”

Still, statewide figures such as those complied in the Atlas can obscure as much as they reveal. Better to look at the detailed counts from individual survey routes. And it turns out data from BBS Route 46110, the nearest to the Takoma Park and Bethesda sites, actually 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.”)

BBS Data: Gray Catbirds Along Route 46110BBS Data: Gray Catbirds Across Route 46110 (adapted from North American Breeding Bird Survey website)

All of which has me wondering about Marra’s rather dire forecast for the area’s gray catbirds—in terms of the underlying science, of course, but also the possible motives behind such a statement.

*     *     *

Publishing dodgy science within the scientific community is one thing—hardly excusable, but there is at least a reasonable expectation that one’s peers are in a position to critically evaluate such research—but to package this kind of work for public consumption is truly irresponsible. Like Higgins’ column, “Baby Catbird Survival” is a Trojan Horse: unsubstantiated—and, potentially, highly damaging—claims “wrapped up” as valid science.

Brilliant from a marketing standpoint, maybe—but it’s hardly my idea of leadership.

I’ve attempted to contact both the SMBC and Peter Marra—expressing my concerns with “Baby Catbird Survival,” but also my interest in a more complete accounting of the study’s findings. Unfortunately, neither has responded.

SPECIAL THANKS once again to Louise Holton and Maggie Funkhouser at Alley Cat Rescue for bringing the Washington Post article to my attention.

Literature Cited
1. Seife, C., Proofiness: The Dark Arts of Mathematical Deception. 2010: Viking Adult.

2. Lepczyk, C.A., et al., “What Conservation Biologists Can Do to Counter Trap-Neuter-Return: Response to Longcore et al.” Conservation Biology. 2010. 24(2): p. 627-629.

3. Churcher, P.B. and Lawton, J.H., “Predation by domestic cats in an English village.” Journal of Zoology. 1987. 212(3): p. 439-455.

4. Woods, M., McDonald, R.A., and Harris, S., “Predation of wildlife by domestic cats Felis catus in Great Britain.” Mammal Review. 2003. 33(2): p. 174-188.

5. Baker, P.J., et al., “Impact of predation by domestic cats Felis catus in an urban area.” Mammal Review. 2005. 35(3/4): p. 302-312.

6. Baker, P.J., et al., “Cats about town: is predation by free-ranging pet cats Felis catus likely to affect urban bird populations? Ibis. 2008. 150: p. 86-99.

7. Barratt, D.G., “Predation by house cats, Felis catus (L.), in Canberra, Australia. II. Factors affecting the amount of prey caught and estimates of the impact on wildlife.” Wildlife Research. 1998. 25(5): p. 475–487.

8. ABC, Human Attitudes and Behavior Regarding Cats. 1997, American Bird Conservancy: Washington, DC. http://www.abcbirds.org/abcprograms/policy/cats/materials/attitudes.pdf

9. Clancy, E.A., Moore, A.S., and Bertone, E.R., “Evaluation of cat and owner characteristics and their relationships to outdoor access of owned cats.” Journal of the American Veterinary Medical Association. 2003. 222(11): p. 1541-1545.

10. Lord, L.K., “Attitudes toward and perceptions of free-roaming cats among individuals living in Ohio.” Journal of the American Veterinary Medical Association. 2008. 232(8): p. 1159-1167.

11. APPA, 2009–2010 APPA National Pet Owners Survey. 2009, American Pet Products Association: Greenwich, CT.

12. Tabor, R., Cats—The Rise of the Cat. 1991, London: BBC Books.

13. Leyhausen, P., Cat Behavior: The predatory and social behavior of domestic and wild cats. Garland series in ethology. 1979, New York: Garland STPM Press.

14. Fitzgerald, B.M. and Turner, D.C., Hunting Behaviour of domestic cats and their impact on prey populations, in The Domestic Cat: The biology of its behaviour, D.C. Turner and P.P.G. Bateson, Editors. 2000, Cambridge University Press: Cambridge, U.K.; New York. p. 151–175.

15. Turner, D.C. and Meister, O., Hunting Behaviour of the Domestic Cat, in The Domestic Cat: The Biology of Its Behaviour, D.C. Turner and P.P.G. Bateson, Editors. 1988, Cambridge University Press: Cambridge.

16. Thompson, B., The Backyard Bird Watcher’s Answer Guide. 2008: Bird Watcher’s Digest.

17. Bird, D.M., Crouching Raptor, Hidden Danger, in The Backyard Birds Newsletter. 2010, Bird Watcher’s Digest.

18. Robbins, C.S. and Blom, E.A.T., Atlas of the breeding birds of Maryland and the District of Columbia. Pitt series in nature and natural history. 1996, Pittsburgh, PA: University of Pittsburgh Press.

Inside Job II

Another study demonstrates that the majority of pet cats spend their time indoors.

In my previous post on the subject, I somehow overlooked Linda Lord’s paper, “Attitudes toward and perceptions of free-roaming cats among individuals living in Ohio.” [1] In it, Lord, Assistant Professor in Ohio State University’s College of Veterinary Medicine, presents the results of an extensive 2007 telephone survey.

Fifty-nine percent of the 217 cat owners participating in the study reported that their cats were indoor-only. Nearly 20% more allowed their cats outdoors no more than three hours each day.

Linda Lord Indoor-Outdoor Data

Lord’s results are very much in line with findings from the three studies I cited previously. [2–4] All of which contradict the bogus claims made recently by Washington Post columnist Adrian Higgins, and last year by Nico Dauphiné and Robert J. Cooper (download their Partners in Flight conference paper here). [5]

These findings also raise questions about a comment made by Pete Marra in the Post story. Referring to his recent investigation into the mortality of catbird fledglings, Marra suggests that the culprits “aren’t feral cats; they’re domestic cats allowed to go outside.” I’ll take a closer look at Marra’s study in my next post…

Literature Cited
1. Lord, L.K., “Attitudes toward and perceptions of free-roaming cats among individuals living in Ohio.” Journal of the American Veterinary Medical Association. 2008. 232(8): p. 1159-1167.

2. Clancy, E.A., Moore, A.S., and Bertone, E.R., “Evaluation of cat and owner characteristics and their relationships to outdoor access of owned cats.” Journal of the American Veterinary Medical Association. 2003. 222(11): p. 1541-1545.

3. ABC, Human Attitudes and Behavior Regarding Cats. 1997, American Bird Conservancy: Washington, DC. http://www.abcbirds.org/abcprograms/policy/cats/materials/attitudes.pdf

4. APPA, 2009–2010 APPA National Pet Owners Survey. 2009, American Pet Products Association: Greenwich, CT.

5. Dauphiné, N. and Cooper, R.J., Impacts of Free-ranging Domestic Cats (Felis catus) on birds in the United States: A review of recent research with conservation and management recommendations, in Fourth International Partners in Flight Conference: Tundra to Tropics. 2009. p. 205–219. www.pwrc.usgs.gov/pif/pubs/McAllenProc/articles/PIF09_Anthropogenic%20Impacts/Dauphine_1_PIF09.pdf

Garden Tool

The timing was uncanny. Four days after my post “Inside Job,” Washington Post columnist Adrian Higgins reported incorrectly that two-thirds of pet cats are allowed outdoors. Higgins doesn’t mention where he got that figure, but considering the sources he used for the piece—including the American Bird Conservancy (ABC), The Wildlife Society, and Dauphiné and Cooper’s 2009 Partners in Flight paper—it’s not hard to sort out.

Ditto for his matter-of-fact assertion that “the cumulative effect on birds is significant, according to experts.” Higgins relies on Dauphiné and Cooper for estimates of both the number of “stray and out-and-out feral cats” (“there may be as many as 100 million such cats in the country”) and birds killed by free-roaming cats (“at least one billion birds are killed by cats annually, ‘and the actual number is probably much higher.’”). [1]

Higgins’ column appeared exactly one week after the release of Charles Seife’s book Proofiness: The Dark Arts of Mathematical Deception. Proofiness, writes Seife, is “the art of using bogus mathematical arguments to prove something that you know in your heart is true—even when it’s not.” [2]

Many—perhaps most—of the scientific claims made by opponents of free-roaming cats/TNR are textbook cases of proofiness. Nevertheless, they are often accepted at face value by the media, which—simply by passing them along for public consumption—gives these assertions unwarranted credibility.

Pete Marra
The central character in Higgins’ story is Pete Marra, a fellow gardener and a research associate at the Smithsonian Conservation Biology Institute. Marra’s name rang a bell.

Sure enough, this is the same Peter P. Marra who, along with nine others (including Dauphiné and Cooper), authored a comment in Conservation Biology earlier this year, entitled “What Conservation Biologists Can Do to Counter Trap-Neuter-Return: Response to Longcore et al.” (the publication of which prompted a series of Vox Felina posts, beginning with this one).

What Marra and his co-authors penned is an unapologetic call to action:

Proponents of TNR are well organized and push for TNR-friendly policies in communities and shelters around the United States, often with little opposition from the conservation biology and wildlife ecology communities… Regardless of why the scientific and management communities have remained relatively silent, it is imperative that we now begin speaking out. [2]

As I have argued, the silence that so frustrates Marra and the others may simply reflect the fact that so much of the work he and his colleagues defend is largely indefensible. Indeed, “What Conservation Biologists Can Do” is, in its own way, representative. Consider the authors’ comparison of TNR with hoarding:

The animal welfare community opposes “cat hoarding,” whereby people care for more pets than they can adequately support, because it is considered inhumane. Trap-neuter-return is essentially cat hoarding without walls. Considering that most communities have laws banning animal hoarding, we should consider the same standard for outdoor cats as those that are in a person’s home. [3]

But their interest in using the law to put a stop to TNR doesn’t end there. Marra and his colleagues continue:

…it may become incumbent upon us to take legal action against colonies and colony managers, particularly in areas that provide habitat for migratory birds or endangered species. [3]

The authors quote a 2003 article written by Linda Winter, the former director of the ABC’s Cats Indoors! campaign, for the Hawaii Audubon Society newsletter:

“…releasing cats into the wild and supporting feral cat colonies is a violation of the Migratory Bird Treaty Act and the Endangered Species Act, as well as laws prohibiting animal abandonment.” (her emphasis, not mine) [4]

As a frequent critic of Winter’s writing, I was eager to read the newsletter (which can be downloaded here). It turns out Winter was referring to a 2003 report submitted by Pamela Jo Hatley—then a student in the University of Florida’s Levin College of Law and part of its University of Florida Conservation Clinic—to the U.S. Fish & Wildlife Service.

Winter—and by extension, Marra and his colleagues—are unambiguous on this point: TNR is a clear violation of both the Migratory Bird Treaty Act and the Endangered Species Act. But, of course, law students don’t make legal decisions; that’s what we have courts for (which might explain why, years later, Travis Longcore and his Urban Wildlands Group took a rather different approach in their TNR-related lawsuit against the City of Los Angeles).

But back to Hatley—there’s another familiar name. In fact, I’d seen it right beside Marra’s earlier this year. See, Pamela Jo Hatley is one of the 10 co-authors of “What Conservation Biologists Can Do.”

So why didn’t the authors just cite Hatley’s work directly, rather than turning to Winter’s version of it? Simply put, Winter’s version is a better story—short and sweet, and brimming with certitude.

But if Marra and the others—Hatley included—wanted to distance themselves from the original, it’s understandable. Though her legal arguments are somewhat compelling, Hatley’s report is a minefield of misrepresentations, flawed estimates, and unsubstantiated claims where the science is concerned (e.g., extrapolating the Wisconsin Study to Florida, and then suggesting that “the actual number [of birds killed by cats in the state] may be much higher” [5]). In other words, more proofiness.

Its title, Feral Cat Colonies in Florida: The Fur and the Feathers Are Flying, is a good indication of how seriously the report—ostensibly a formal document submitted to a federal agency—should be taken.

Getting Dirty
To read Higgins’ column in the Post, one gets the idea that he and Marra are merely fellow gardeners, perhaps having bumped into each other at the local nursery or hardware store. And that’s where the story began. It could be.

But there’s a sentence in “What Conservation Biologists Can Do” that’s been bothering me ever since I read Higgins’ piece:

Conservation biologists have just as much opportunity to make their points at local meetings, through the news media, and at outreach events as do TNR proponents. (emphasis mine) [2]

I have no idea whether Higgins and Marra knew each other before Higgins began work on his column, or how Higgins feels about cats. And I’m not one to go in for conspiracy theories, either.

What I am sure of is that Higgins—as a journalist—should have done his homework. He did not. (To be fair, Higgins did speak with Alley Cat Allies; but “equal time” is a poor substitute for accuracy.) And the consequences of his carelessly scattering a few figures around a column devoted to gardening are considerable: the seeds of proofiness!

Maybe readers don’t expect Higgins to know (or care, even) how many free-roaming cats there are in the U.S. Or how much time pet cats spend outdoors. Still, though, Higgins is an avid gardener—he, of all people, should be able to recognize bullshit.

*     *     *

SPECIAL THANKS to Louise Holton, founder of Alley Cat Rescue, who brought the Washington Post article (along with countless other news items over the past few months!) to my attention. She and Maggie Funkhouser, ACR’s Director of Communications and Public Relations, have become invaluable resources.

Literature Cited
1. Higgins, A., Bird lovers see roaming cats as a major threat to many species, in The Washington Post. 2010: Washington, DC. http://www.washingtonpost.com/wp-dyn/content/article/2010/09/28/AR2010092803999.html

2. Seife, C., Proofiness: The Dark Arts of Mathematical Deception. 2010: Viking Adult.

3. Lepczyk, C.A., et al., “What Conservation Biologists Can Do to Counter Trap-Neuter-Return: Response to Longcore et al.” Conservation Biology. 2010. 24(2): p. 627-629.

4. Winter, L., “Popoki and Hawai’i’s Native Birds.” ‘Elepaio: Journal of the Hawaii Audubon Society. 2003. 63(6).

5. Hatley, P.J., Feral Cat Colonies in Florida: The Fur and the Feathers Are Flying. 2003, University of Florida Conservation Clinic: Gainsville, FL.