Nearly four years before the terms fake news and alternative facts made their way into common usage, there were Peter Marra’s mortality “estimates.” Developed at great expense to taxpayers, Marra’s computer-generated figures suggest that outdoor cats kill up to 4.0 billion birds annually in the 48 contiguous states.  Even without getting into the details, it should be obvious that the claim is simply nonsense—since the best estimates available indicate that there are only 3.2 billion birds in the continental U.S.
Nevertheless, with the publication of Cat Wars: The Devastating Consequences of a Cuddly Killer late last year, Marra doubled down on his “estimates,” making this tidy bit of fiction the centerpiece of his campaign of misinformation, scaremongering, and magical thinking.
All of that seems like a lifetime ago now—before Donald Trump became President, and, together with his largely inexperienced and woefully unprepared staff of cronies, plunged us into a Bizarro World. Up is down, black is white, right is wrong. Foreign policy is made and unmade in 140-character outbursts.
Not to be outdone, Marra’s stepped up his game—misrepresenting his own work (which, again, was junk science to begin with) and proposing a new theory of urban ecology.
Our National Bird Deficit
Appearing last week on WTTW’s Chicago Tonight, Marra was asked to comment on Chicago’s “working cat” program, in which cats with poor adoption prospects are sterilized, vaccinated, and “hired out” to help address the city’s rat population. But first, host Phil Ponce asked him to give the audience a “sense of the impact [cats] have on the natural environment.” Although Ponce had already referred to the infamous 4.0 billion “estimate,” Marra repeated the figure and, after a brief pause, added for emphasis, “native species of birds.”
Really? That’s not what he and his co-authors claimed four years ago, when they attributed “33 percent of bird prey items identified to species were non-native species in 10 studies with 438 specimens of 58 species.” [1, emphasis mine]
Was it not enough that he was already claiming cats kill more birds than actually exist? Apparently not. Besides, what are the chances the mainstream media would dig deep enough to call him out? Especially when there are props in the form of taxidermied bird specimens—including a wood thrush, which Marra explained, is “another example of a species that’s commonly preyed upon by cats.”
Here again, Marra’s statement is contradicted by his own writings.*
In the 2013 paper he and Cat Wars co-author Chris Santella describe as a “groundbreaking study” resulting from a careful review of “hundreds of studies,”  just one of the studies compiled mentions the wood thrush. And that study documented exactly one wood thrush death, while researchers observed five cats over the course of 11 months. 
But we’re expected to believe this species is “commonly preyed upon by cats”? It would seem so.
An Emerging Theory of Urban Ecology
When at last Marra weighs in on Chicago’s rats, he concedes nothing. “That’s a tremendous mistake, to take an invasive predator and use it as a form of bio-control on another invasive predator,” says Marra. “It’s just creating one problem with another problem.”
And here, Marra seems to go off-script.
“The fact of the matter is, many of those cats are probably not preying on those rats—they’re just dispersing those rats, and causing a problem elsewhere. Those rats need to be dealt with… at the source. We need to get the food under control, we need to get water under control, we need to make sure wherever those rats are going—we need to get that under control. We need to use rodenticides.”
Setting aside for a moment the Sisyphean challenges associated with getting the food and water (e.g., Lake Michigan) “under control” in Chicago (or any other urban area), and Marra’s endorsement of rodenticides (a cause of great concern among his fellow ornithologists), I’m struck by Marra’s fantastic theory that cats merely disperse rats but decimate birds (which, in most cases, have the distinct advantage of flight).
One wonders if this is peculiar to cats, or if the same true of other predators—including, say, avian predators? One thing’s for sure: if anybody can publish a paper promoting such a theory (written mostly by a publicly funded post-doc, no doubt), it’s Peter Marra. Or maybe he’ll turn to the platform of choice for such things, and publish via an early-morning Tweet.
* Marra’s former colleague, Nico Dauphiné, was prone to the same problem. Indeed, her habit of egregious double-speak during a 2011 trial for attempted animal cruelty earned Dauphiné a guilty verdict, after which she lost her prestigious fellowship with the Smithsonian’s Migratory Bird Center.
1. Loss, S.R., T. Will, and P.P. Marra, The impact of free-ranging domestic cats on wildlife of the United States. Nature Communications, 2013. 4 http://www.nature.com/ncomms/journal/v4/n1/full/ncomms2380.html
2. Marra, P.P. and C. Santella, Cat Wars: The Devastating Consequences of a Cuddly Killer. 2016: Princeton University Press.
3. Mitchell, J.C. and R.A. Beck, Free-Ranging Domestic Cat Predation on Native Vertebrates in Rural and Urban Virginia. Virginia Journal of Science, 1992. 43(1B): p. 197–207. http://www.vacadsci.org/vjsArchives/v43/43-1B/43-197.pdf