What is with the taxidermied animals and birds Norman Bates had in Psycho?

Norman Bates (Anthony Perkins) in pyscho is what the title implies. He is a psyschopath… A human monster. A psychopath is described as follows on Wikipedia:

Psychopathy, also known as—though sometimes distinguished from—sociopathy, is traditionally defined as a personality disorder characterized by enduring antisocial behavior, diminished empathy and remorse, and disinhibited or bold behavior.

Knowing that Norman Bates is an antisocial loner who lacks empathy, let’s think about the big reveal at the end of the film: His “mother” has been dead for years and is a desiccated corpse that he keeps in their home/hotel.

Norman clearly has no idea what life is and has no empathy; living things are just objects to him. His mother is dead but the remains of his mother are kept in the home because… That is his mother. When he acts out in rage he might act like the mental image he has of his overbearing mother—that’s my interpretation—but the corpse is still cared for.

Now look at those taxidermied birds. They are dead to you and me, right? But to Norman those taxidermied birds are his companions… Just like the dead and lifeless corpse of his mother. They are superficially “things” but they sure as hell not life.

Also, those taxidermied birds can be seen as trophies since traditionally that is what taxidermy is: Taking the remains of something you hunted and killed and creating a trophy of what you have to show off what you did. This snippet of dialogue sums up Norman’s bizarre realtionship with the birds as well:

Norman Bates: You-you eat like a bird.

Marion Crane: [Looking around at the stuffed birds while eating] And you’d know, of course.

Norman Bates: No, not really. Anyway, I hear the expression “eats like a bird” - it-it’s really a

[stammers]

Norman Bates: fals-fals-fals-falsity. Because birds really eat a tremendous lot. But -I-I don’t really know anything about birds. My hobby is stuffing things. You know - taxidermy.

So let’s get this straight: He’s antisocial, but his attempt at small talk is to tell Marion Crane (Janet Leigh) is to say she “eats like a bird.” Her response is to compliment his knowledge by acknowledging his taxidermy. And then he says he doesn’t really know anything about birds but his hobby is “stuffing things?” You don’t stuff a bird without that bird being dead, right? So his hobby is killing things and he has no idea what birds are about anyway. He just likes to kill them.

Well there you go! He has no idea what life is… He just likes to deal with—or create death—and keep trophies/mementos of things.

Also, this blog post does a nice bit of storytelling/symbolism analysis of the meaning of the taxidermied animals; bold emphasis is mine:

In this parlor scene, we understand the meaning behind the bird motif. The birds are representative of each characters personality. The different species of birds represent the different elements of Norman and Marion’s personalities. Besides her last name being that of a bird, Marion draws several comparisons to birds in this scene. By saying she eats like a bird and having her surrounded by little finch like birds, we see her as vulnerable thus increasing the suspense for the viewer. As for the crow that is above her, that could represent her guilt for stealing the money, or provide foreshadow for her eventual demise. Norman is represented by two different set of birds as well; the large yet timid birds, and great owl above his head. The shy and socially awkward side of Norman and the murderous mother personality represent those birds respectively. When he is calm the bird in site (sic) is the turkey, which is far from intimidating. When his personality switches, we see the looming predator owl above his head. The aggression in his tone is matched by the owl, which is threatening to the viewer in its size and opened winged pose. Before Norman looks into the peep hole, we see both types of birds used to represent his personality, indicating a split in his personality. The metaphor of birds is represented of the different personalities of the characters and the danger associated with these traits.