When his dead mother appears in the wheelchair and the viewer realizes he has been recreating her voice himself, and the sheriff confirms this as he relates Norman's story. While "The Birds" ends relatively happily, at least the main characters survive; "Psycho" ends with Norman in a jail cell. All the loose ends are wrapped up, but in one, the end is dark and disturbing, while in the other, there is hope. Psycho," made in 1960, is shot in stark black and white, which somehow seems to enhance the feeling of terror, because Hitchcock is a master of setting, mood, and lighting, as well. "The Birds," made in 1963, is shot in color, making it seem more modern, and all the more terrifying because the blood from the bird attacks seems more real and menacing, somehow. Hitchcock uses actors who can seem like normal, everyday people with normal everyday feelings and emotions to make them seem real to the audience, and he builds tension by creating scenes where normal activities are intertwined with very abnormal ones. In one scene in "The Birds," Melanie sits outside the school...

The same is true of the shower scene in "Psycho." Taking a shower is a very normal activity, but the tension builds as the door opens and a knife appears, and then reaches through the shower curtain. The music in this scene punctuates the violence and the murder, and Hitchcock uses it well, it is as memorable as the scene itself.
In conclusion, these films have a lot in common, and some very specific differences. They both show the talent and imagination of Alfred Hitchcock, who may be one of the greatest horror directors ever in history.

References

Psycho. Dir. Alfred Hitchcock. Perf. Anthony Perkins and Janet Leigh. Paramount Pictures, 1960.

The Birds. Dir. Alfred Hitchcock. Perf. Rod Taylor, Jessica Tandy, Suzanne Pleshette and Tippi Hedren. Universal Pictures, 1963.