Cats kill birds: keep 'em inside

One in every ten birds in the United States will see the same thing just before death: a cat. We now know that the effect of cats goes well beyond killing. English researchers demonstrated that a parent bird reduces the rate at which it feeds nestlings when it glimpses a cat. Reduced feeding may result in undersized young, but more important, the unattended nest becomes easy prey for jays and crows. . . . Stewarding our urban birds requires that we keep cats indoors. Period. (It's safer for the cats as well.)

John M. Marzluff, Welcome to Subirdia: Sharing Our Neighborhoods with Wrens, Robins, Woodpeckers, and Other Wildlife (New Haven: Yale Univ. Press, 2014), p. 59