Symbolism, Imagery, Allegory
That Victorian England sure is a dog-eat-dog world, er, dog-eat-bird world, er, bird-eat-dog world, er, bird-eat-bird world. In any case, it's hunt or be hunted. It's prey or be preyed upon. It's vicious.
One of the joys of reading Dickens is that the bad guys are really, really bad. You can hate-read to your heart's content… his villains are just so villainous. And Our Mutual Friend is no exception. Dickens makes the game of spot-the-bad-dude really easy: he compares the baddies outright to birds of prey.
Check out our introduction to Gaffer:
He was a hook-nosed man, and with that and his bright eyes and his ruffled head, bore a certain likeness to a roused bird of prey. (1.1.12)
Watch out, everybody. Gaffer's not just hawk-looking—he's roused. Other birds of prey in this book include Mr. Riderhood, Silas Wegg, and Mr. Fledgeby. Yup: the whole cast of Big Bads ain't wolves. They're hawks, eagles, and falcons.
This says a little something about Dickens view of what evil is. For Dickens, evil isn't tied to strength or ferociousness. It has nothing to do with keeping your temper or flying off the handle. The root of evil in Our Mutual Friend is being predatory: looking for the next opportunity to manipulate, to get a leg up, or to shoot down an opponent.