"There are many peaceful and monogamous birds in the Animal Kingdom who provide a model for loving human relationships. Mourning doves, sparrows, and finches all have their tender and caring courting rituals and share jointly in the nurturing and protecting of their young.
There are, however, a few bad birds. And the baddest of the bird world Bad Boys is the rare male great tit (Parus Calioptrus). Ornithologists are usually excited when the see a pair of great tits in the wild, as you can well imagine.
It should come as no surprise to anyone who's ever had to suffer through an episode of Benny Hill that the great tits make their home in England. While there are also blue tits and mouse tits it is the great tits who are notorious for being among the very few songbirds that actually murder other songbirds. Male great tits have actually gotten so aggressive that they will steal food from humans, using their sharp beaks to open freshly delivered bottles of milk on people's doorsteps.
You'd think great tits would have their own milk, but of course, they don't.
This tendency for great tits to go wrong (thus becoming killer tits) is avenged only when they themselves become victims of larger birds of prey like hawks or owls. There is almost no sight in nature as ugly as a battle to the death between a pair of big hooters and some killer tits."
-Cathryn Michon, The Grrl Genius Guide to Sex (with Other People)
Pages 36-37, First Edition, copyright 2004