"How many American cats live largely or entirely outdoors? (More than a hundred million.) What proportion of them kill birds? (More than half.)"

"And how many birds does a bird-killing cat kill in one year? (Perhaps three dozen.) Each of these multipliers had a range of uncertainty, so the model needed to be run repeatedly. The number it generated most often was 2.4 billion birds a year. Outdoor-cat advocates were quick to dismiss the paper as 'junk science.'... But I, too, at first, being skeptical of models, had trouble believing that the numbers could be so vast.... The most dismal number in the Nature Communications paper was its median estimate for the birds killed annually by cats with owners: six hundred and eighty-four million. Unlike the death toll from unowned cats, this number could be zero, because tame cats can be kept indoors.... I... have friends who, if I suggest that they might not want to let their cats outside, respond not with rationales but with uneasiness. My guess is that, just as I will sometimes eat a tuna sandwich, despite knowing what I know about tuna fisheries, my friends are doing a small thing that they know isn’t right but is convenient. In a darker way, I wonder if one of the attractions of having cats as pets is precisely that, however affectionate they may be, they have a savage side as well, sharp of tooth and keen of claw...."

Writes Jonathan Franzen, in "How the 'No Kill' Movement Betrays Its Name/By keeping cats outdoors, trap-neuter-release policies have troubling consequences for city residents, local wildlife—and even the cats themselves" (The New Yorker).

Much more from Franzen — the great novelist and bird defender — at the link.