This opening appears more like a romantic comedy than a horror picture because of the flirtatious meeting between Mitch and Melanie. There is no feeling of dread or fear, except for a foreboding from the large flock of sea gulls and their loud cries outside. Once inside, however, the birds do not appear to present any kind of threat.
When we first see Melanie, it is apparent that she is stylish and sophisticated (and probably very rich). She is not used to being disappointed, which is obvious with her impatience that the myna bird she ordered is late and won't talk immediately. As she is writing her address at the counter, Mitch enters and innocently assumes she is a sales clerk. However, when she looks up, he seems to recognize her. When she pretends to be the sales clerk, he starts asking her questions that show how little she actually knows about birds. We know that both characters are putting on an act for the other and both are mildly flirting. We also find out that Mitch is there to purchase a pair of love birds for his sister's 11th birthday.
Except for some normal "street noise," all you hear are the sounds of birds. Outside, the birds sound rather ominous, but once Melanie enters the pet shop, the birds inside are chirping pleasantly and provide a nice backdrop to the romantic encounter between Mitch and Melanie.
Hitchcock is seen exiting the pet shop with two small white terriers as Melanie is entering the shop. I don't see any particular meaning in relation to the scene or the story. However, I do think its cute that they are actually Hitchcock's dogs. I guess we all like to show off our pets!