I won first place in this costume last year at our annual Halloween party. This was super easy, comfortable, and cheap. I already owned the tank top and shoes. I bought the dress suit for less than $5 at Goodwill.
I bought all the birds, except for the larger bird on my shoulder at the Dollar store for $1 a piece, I think the larger bird was around $10. I did buy the wig at the Halloween store, it was the only splurge for about $20 and also some fake blood.
To secure the bird to my head I just stuck a thin metal headband that I already had through the Styrofoam body of the bird and it stayed put all night. I sliced random sections of my costume and put the fake blood around them, keeping it simple because Hitchcock movies aren’t about gore. I secured the birds on the suit with hot glue, but some other glue may have worked better since I lost a couple of birds during the night.