Liz Klimas is one of my favorite bloggers in all the world but I can't believe she failed to check the crucial fact in this report:
The crucial fact here is that pet cats are killing all those healthy and valuable adult birds in New Zealand (and in Australia and in Hawaii, and presumably on some South Sea islands from which we haven't heard).
In North America and Europe, all bird species are naturally adapted to coexist with cats--even with wild cats who are much more efficient climbers and hunters than our house pets. (House cats have been systematically bred to be less dangerous, to birds as well as humans, than their wild relatives.)
In Australia, Hawaii, and New Zealand this is not the case...and since we do have a few readers Down Under, let me take this opportunity to recommend that youall keep your cats indoors. You wouldn't want your pet to eat the last living kakapo, right?
But in the contiguous United States, cats are able to attack birds only under two circumstances: (1) when the birds are helpless babies, and (2) when the birds are very, very sick.
If you see a North American cat with a dead adult bird, you should remove the bird from the cat--it will make the cat sick. Don't handle the bird yourself! Wrap and burn it, then wash your hands thoroughly.
Birds can lose their ability to fly for several reasons, including injuries, old age, chemical poisoning, parasites, and bird flu, but the Sibley guidebooks say the most common reason is aspergillosis. Most of the birds I've taken away from my cats were visibly suffering from aspergillosis. Humans rarely develop visible symptoms of this disease unless they have AIDS (in which case the fungus can grow on human skin, just as it does on sick birds' skin, forming patches of green slime) but humans do get allergy and flu-type symptoms as our immune systems cope with this fast-growing infectious fungus.
Helpless baby birds are another good reason to confine cats, but in most of the United States the baby birds are helpless for only a week or two at a time, and by observing your birds you'll know when it's time to bring the cats inside. This happens to be the time of year when field mice and other wild vermin are not highly motivated to destroy your home, if you keep food covered when not in use. Isn't nature wonderful? If you're not a bird watcher or haven't noticed a ground-nesting adult bird flying around your home, but you see a cat with a baby bird, even this web site recommends that you confine that cat--or ask its humans to do so--for another week.
There is one other excuse for interfering with cats' valuable role in limiting rat and mouse populations in the name of protecting birds. That would be if your neighborhood is positively known to be the home of a severely endangered (not merely threatened) bird species. When a species gets down to a few hundred individual birds, then its habitats can fairly be declared bird sanctuaries where even sick individuals need to be allowed every chance to produce healthy eggs. Ornithologists don't necessarily know when and how to confine the sick individuals and/or take the eggs into custody, but they think they do, and denying them their chance to study severely endangered birds is a pointless bit of cruelty.
Otherwise, when North Americans think of cats killing cute little fluttering, twittering songbirds, we need to give thanks that they've put these poor sick individuals out of their misery before the sick birds could endanger others.
RECOMMENDED READING (more about key facts discussed above, and also good reads!)
Endangered birds in Australia and New Zealand: Anybody who likes this web site ought to love Douglas Adams' Last Chance to See. Despite its profanity, gross-outs, and atheist reflections I'd share this one with The Nephews. Close-up looks and a few pictures of some birds that are actually threatened by cats.
Birds in North America: The Sibley Guide to Bird Life and Behavior. If you already have Peterson's Field Guide to Birds of North America, which I find easier to use to look up new birds, check the Sibley guide anyway for more information on nesting habits after you've identified a bird.
Symptoms of full-blown aspergillosis in humans: Jamaica Kincaid's My Brother (he had it). This one is not recommended for children but it's definitely recommended to teenagers contemplating becoming sexually active.