The problem is, the vast majority are taken from the wild, and aren't used to life in cages. Many die soon after they're purchased, but at prices as low as $10, demand is only growing.

"Over half of the owls for sale were not yet adult, with significant numbers apparently being young taken from their nests," the study, published in journal Global Ecology and Conservation, reads.

"At the end of 2016 we identified at least 15 dedicated Facebook groups, with over 35,000 members, six websites, four blogs, one Instagram and two twitter accounts. Pet owl interest groups are present in Jakarta, Malang, Surakarta, Surabaya, Sitoardjo, amongst others, and members meet up in city centres, especially on car-free Sundays, displaying their pet owls and exchanging information."

The researchers say many varieties of owl are now under threat.

"The rise in popularity of keeping owls as pets, and the associated rise of the number of pet owl interest groups, organising themselves on social media, suggests the types of people who now want owls as a pet - and have the means to acquire one - have increased and diversified.

"While what we observed in the bird markets is probably just the proverbial tip of the iceberg."