Hundreds of online forums have appeared, with fans comparing notes on how to obtain the birds. And such is the phenomenon that the Indonesian word for owl, burung hantu, which means ghost bird, is now more commonly known as burung Harry Potter.
Concerned researchers have now called for owls to be included on Indonesia's protected species list.
Professor Vincent Nijman, who co-wrote the paper for the journal Global Ecology and Conservation, warned that ordinary people have no idea how to look after the birds.
He said: "They are alive and cute when you see them on the market, but realistically they are already dead."
Prof Nijman added: "In the 1990s, when surveying the bird markets, I would typically see one or two owls for sale among the thousands of wild-caught birds on offer, but often there was not a single owl on display.
"Now, returning to those same markets, we can see dozens of owls for sale, all taken from the wild."
Researchers found that growing numbers of highly endangered owls were being trapped, traded or killed in black magic rituals. Many other characters in the Harry Potter books also kept owls, including the Weasley family's post owl, Errol, an ancient great grey; Ron Weasley's older brother, Percy, kept a screech-owl; and Harry's nemesis, Draco Malfoy, had a large Eurasian eagle-owl.
Ms Rowling has previously said: "If anybody has been influenced by my books to think an owl would be happiest shut in a small cage and kept in a house, I would like to take this opportunity to say as forcefully as I can, 'You are wrong'."
"If your owl-mania seeks concrete expression, why not sponsor an owl at a bird sanctuary where you can visit and know that you have secured him or her a happy, healthy life."
More than just a pet for the boy wizard, Hedwig is described as Harry's "only friend" at No 4 Privet Drive - the home of his spiteful uncle and aunt, where he is forced to spend his summers.
In an interview, Ms Rowling described the bird as "a cuddly toy to Harry at times".
