Now, cats do a fine job providing companionship and keeping a house mouse-free, and few things bring more instant joy to a room than a laundry basket full of kittens. But outdoors, cats are a massively destructive invasive species, among the worst of the invasive mammals. They kill tens of millions of birds each year in Wisconsin alone; they eat endangered North American species such as the piping plover and least tern; and they have driven many bird species to extinction, including the Auckland Island merganser and the Chatham Island fernbird.
The latest measure of their destruction comes from the Smithsonian Migratory Bird Center, which has been tracking birds that live in the urban and suburban areas in and around D.C. Some neighborhoods, like Takoma Park, have a lot of cats roaming the streets. (I'm not an anti-Takoma-Park bigot; some of my best friends live in Takoma Park.) Other neighborhoods, such as Bethesda, have more responsible, considerate and environmentally friendly cat owners that keep their domesticated predators indoors. In a recent study (pdf) in the Journal of Ornithology, Anne Balogh, Thomas Ryder and Peter Marra report that, basically, birds in cat-dense neighborhoods can forget about raising chicks. Working with the unfortunately named catbird (the bird's call sounds like a meow), the researchers counted eggs, nestlings, adults and fledglings; tagged and radio-collared the birds; monitored their behavior; and counted the bodies. They found that catbird chicks hatch fine, but as soon as they fledge from the nest—bam, the juvenile birds get snapped up by cats. How can the researchers tell which chicks were eaten by cats rather than, say, hawks or squirrels? Cats decapitate their bird prey.
Charming, aren't they? I've tried many methods to keep my neighbors' outdoor cats away from my yard: squirt guns, tennis balls (lobbed, not pitched that hard), clapping my hands, charging them while waving my hands and hissing. The latter, while least dignified, seems to scare them off the longest. (Ed. note -- Sadly, no video of this exists. Yet.) Do you have any tips for keeping the feline monsters away from nature's finest clade, the birds?