
Director Dario Argento was a screenwriter for some years (including co-writing Sergio Leone's classic, Once Upon a Time in the West (1969), and Don Taylor's 1970 Western, Five Man Army). The Bird with the Crystal Plumage (1969) was his directorial debut and marked the beginning of what would become his trademarks. These include: a killer who threatens people with a creepy, whispering voice; focusing on the killer's weapon(s) of choice with extreme close-ups; and frequent point-of-view shots of the killer donning black leather gloves (Argento has stated that, in his films, the killer's hands always belong to the director himself, who believes that no one else can move the hands the way that he wants). One of the more significant and original trademarks that Argento first employed in his debut is a character who believes that he/she has seen something that may be important, but cannot be recalled at the present time. Sam says just that in The Bird with the Crystal Plumage, that there was something about the attack that was a little "off." Argento did this again in films such as 1975's Deep Red (aka The Hatchet Murders), 1982's Tenebrae (aka Unsane), and Trauma (1992). In each film, the character invariably remembers what exactly he/she was seeing, and it eventually leads to the killer's unmasking.

The unveiling of the murderer is shocking and quite clever, and it's important to note that Argento never cheats in hiding the killer's identity. He is fair in his presentation to the audience. Much like the protagonist, Sam, the viewers see what they need to see and are allowed to form their own conclusions. Although many Italian horror films are mocked for weak and illogical stories (as well as shoddy English dubbing), The Bird with the Crystal Plumage has a solid plot with strong, likable characters. Tony Musante is very good as Sam, but he is outshined by Suzy Kendall portraying Julia. The real star, however, is Argento's camera, which simply refuses to sit still, creating beautifully fluid shots.
The Bird with the Crystal Plumage is reportedly an uncredited adaptation of Frederic Brown's novel, The Screaming Mimi (officially adapted in 1958 in the U.S. as Screaming Mimi). This movie is the start of a reputed "Animal Trilogy," as the director followed this with The Cat o' Nine Tails (1970) and Four Flies on Grey Velvet (1971). Many Italian directors, hoping to achieve similar success, began including animals in the titles, such as Sergio Martino's The Case of the Scorpion's Tail (1971), Paolo Cavara's Black Belly of the Tarantula (1971), and Lucio Fulci's A Lizard in a Woman's Skin (1971) and Don't Torture a Duckling (1972).