Headscratchers / The Birds

• Why did Melanie pretend she worked at the bird shop at the beginning?
  • To get Mitch's attention, and because she likes playing practical jokes.
  • Actually if you watch the scene, Mitch is the one who sets it up by pretending that he thinks Melanie works there (he knows fully well who she is and that she doesn't). Melanie is immediately taken with him and you can see her looking confused before she decides to roll with it as an excuse to talk to him. That scene is there to establish that Melanie has a very mischievous sense of humor, and loves elaborate pranks - which is why she goes to such lengths to deliver the love birds to Cathy. Melanie also seems like a compulsive liar - inventing a fake friendship with Annie for one - with a proud streak, as Mitch busts her for not knowing anything about birds multiple times in that one scene and she keeps on going with the ruse.
• Is there any truth to the theory that Annie is Cathy's biological mother.
  • The theory seems to stem from the huge age difference between Mitch and Cathy - Mitch is clearly late twenties-to early thirties, and Cathy is barely into her teens (there's at least a fifteen year difference) - and how old Lydia seems to be. If you take Jessica Tandy's real age into account, she was in her mid-fifties when the film was made. So doing the math with when Cathy was born puts her at forty-something (possibly thirty-something if she's meant to be younger). People also point to Annie's protective streak towards Cathy - which really could be from the fact that she's her teacher, so of course she'd want to protect her students. And it's only a coincidence that Annie dies saving Cathy; the two are taking Cathy's friend Michelle home and it's then that they're attacked. Annie living in town and not taking care of Cathy if she's her daughter seems a bit too elaborate - especially given that the 60s did see more liberal views for women coming about. Surely if she'd gotten pregnant with Cathy, she and Mitch could have quickly married instead?
    • And while Lydia is possessive, she's not abusively so. She doesn't seem like the type who'd force a woman to abandon her child to avoid a minor scandal just because she's afraid of being left alone.
  • For what it's worth, Annie Hayworth in the original script was going to be an older woman who just lived in the town. Hitchcock made her younger because he liked Suzanne Pleshette (who was lobbying for the role of Melanie) and then added in the backstory of her being Mitch's ex-girlfriend. So his intent from the start was that Cathy was just a daughter of Lydia's who was a lot younger than Mitch.
  • Annie being Cathy's biological mother would also require her to have known Mitch for at least eleven years. Suzanne Pleshette was only twenty-seven, placing Annie's age to thirty at the oldest - which means she would have been quite young to meet Mitch in San Francisco (although they could be college friends if you want to stretch that). Annie never says how long she's lived in Bodega Bay, but we can assume it was after Mitch's father died, since Lydia wouldn't be as possessive of Mitch if her husband were still alive, would she?
• Why did Melanie go upstairs when she was attacked by the birds?
  • Tippi Hedren asked the same thing. She wanted to know her character's motivation and only got "your salary" in response.
  • Perhaps Melanie was just overconfident. She escaped the bird attacks about four times already that day, and might have assumed she could handle a problem if there was one. She is shown to be fiercely independent, so it would be in-character for her to try and do something dangerous on her own.
  • Melanie might also be cracking up from the events of the whole weekend. What started as a quick trip for a practical joke has suddenly turned into a national disaster, where she's literally barricaded in a house for her own safety with complete strangers. It wouldn't be surprising if her judgment was affected by the chaos going on around her.