There’s an analysis here: http://sutroforest.com/2011/04/09/cats-catbirds-why-the-smithsonian-study-doesnt-say-what-everyone-thinks-it-does/

Regarding the “tens of millions of birds [killed by cats] each year in Wisconsin alone,” you and your readers might be interested to know that there actually was no “Wisconsin Study,” as it’s often called–not in the scientific, peer-reviewed-publication sense. The often-cited “estimates”–which have, over the past 15 years, taken on mythical status–were nothing more than biased, back-of-the envelopes guesses.

Indeed, co-author Stanley Temple himself admitted that their figures weren’t “actual data,” though the American Bird Conservancy (ABC), U.S. Fish & Wildlife (USFWS), and others— continue treating these figures as if they were actual data. “That was just our projection to show how bad it might be,” noted Temple.

But Temple wasn’t as forthright about the origins of their “estimates.” The authors’ “intermediate” estimate, for example, was–in addition to its several flawed assumptions– based on the hunting habits of a single rural cat in Virginia. And their high estimate was even less sound.

To your comments about the catbird research—again, you’re doing your readers a disservice.

“The juvenile birds get snapped up by cats”? Actually, the researchers witnessed exactly SIX catbird deaths due to predation by cats. Six of 42 total mortalities.

They attributed THREE more to cats on the basis of decapitated remains because, as they explain, “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 at all uncommon with owls, grackles, jays, magpies, and even raccoons.

Something else Marra and his colleagues fail to acknowledge (let’s face it: it does kind of ruin the story) is how well gray catbirds are actually doing in the area. The North American Breeding Bird Survey indicates that Maryland’s gray catbird population has increased about 9 percent between 1966–2009, a period during which the state’s human population grew approximately 57 percent. And data from BBS Route 46110, the nearest to the research sites, also trend upward in recent years.

Even the Smithsonian Migratory Bird Center, Marra’s employer, 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.”

Given how poorly the Smithsonian has covered this story (beginning last October), it’s difficult not to conclude that the people involved are far more interested in perpetuating the shameful witch hunt against feral cats than they are in promoting rigorous scientific inquiry.

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

Same for the Chatham Island fernbird. Wikipedia: “The reasons for it’s extinction were apparently the brush fires, the overgrazing by goats and rabbits and the predation by rats and feral cats. The last specimen was shot for a collection by Lionel Walter Rothschild in 1895 and it was regarded as extinct by 1900.”

A huge problem with the Smithsonian paper is there was no control group. The scientists took blood samples from the birds and glued radio transmitters to their backs. Probably leaving them compromised, but without a control group, we’ll never know.
My goodness and this nonsense about cats decapitating their prey. Please just a bit of research by the authors would of shown that owls and grackles would have been much more likely suspects than cats. That is, unless that’s not the answer you’re looking for.
Just a few of the articles/books that detail owl prey decapitation:
Bird, D.M., Crouching Raptor, Hidden Danger, in The Backyard Birds Newsletter. 2010, Bird Watcher’s Digest. “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.” Interestingly, the author, David M. Bird, has co-authored another article with Peter Marra.

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

The Marin County breeding bird atlas, W. David Shuford, Point Reyes Bird Observatory, 1993, 475 pages
Snippet: “Year round, Spotted Owls regularly cashe decapitated and partially eaten remains of excess prey and later retrieve them. They securely wedge the remains for storage on top of limbs in trees or on the ground beside logs, trees…”

Live blind snakes in eastern screech owl nests: a novel commensalism. F.R. Gehlback and R.S. Baldridge, 1987, Oecologia, Vol 71, No. 4. “Like most raptorial birds, eastern screech owls kill and usually decapitate vertebrate prey before bringing it to nests.”

Caching behavior of screech owls in Indiana ,JB Cope – The Wilson Bulletin, 1978
“Twenty-two dead chicks, 7 decapitated, were found on a shelf near the ceiling of the enclosure.”