It has been alleged that Tony Musante - known for his intensity and preparedness as an actor - would frequently show up at Dario Argento's apartment at 3 am to discuss characterization, much to Argento's annoyance.
The painting the killer buys from the antique store heavily resembles Pieter Bruegel the Elder's The Hunters in the Snow.
The "Hornitus Nevalis" bird species doesn't actually exist. The one seen in the film is played by a Grey Crowned Crane.
This played in a Milan cinema for 3 and a half years, such was the film's popularity in its native Italy.
Although 'The Bird with the Crystal Plumage' isn't the first Giallo movie, it is credited for making the sub-genre famous and starting the trend that boomed from 1970 to 1975.
Dario Argento: body doubling as the killer. Every shot of those black, leather gloves, as it was far more convenient for him, knowing exactly how to handle the hand movements.