Visible crew/equipment: While Janet Leigh is being stabbed to death by Mother, as Janet turns around in the shower, it is possible to see part of the moleskin that Janet wore for the scene for a split second. (00:47:30)
Visible crew/equipment: When Marion is packing in her room, the camera is panning back over the bed to show the newspaper with the cash wrapped up in it. As the camera pans back, one can see the camera's shadow on the bed.
Visible crew/equipment: When Marion arrives at the car dealership, the salesman sees her and starts walking towards her. If you look carefully, there is a wire trailing out his trouser leg, most likely for a hidden mic.
Visible crew/equipment: When Marion arrives at the car dealership and the salesman says "be with you in a second", pay attention to Marion's car door. You can see the reflection of a crew member kneeling down as soon as she starts walking away from the car.
Chosen answer: Birds are just a favourite choice of spooky animal that Alfred Hitchcock seems to use hence the film "The Birds". Eyes show the window to our soul where our deepest fears originate and who isn't scared of getting knifed in the shower. The mirrors i can't explain but I can suggest that it just looks creepy.