Mistranslations in the Chinese, Japanese, and Vietnamese versions
Hermione, for all her lovable qualities, is regarded as something of a pain in the neck by some of her fellow students. She studies up ahead of class, takes on extra courses, and is devastated by the thought of getting less than 100% in an exam. She is, in fact, a perfect little miss know-it-all.
So it comes as some surprise when Hermione makes the blatantly erroneous assertion that owls are not ordinary local birds in Britain. Or that, at least, is what the Mainland Chinese translation has her say.
The mistake comes when Hermione and Harry are discussing how to get messages to Sirius Black and why Sirius doesn't want Hedwig to deliver them. Hermione comments (in direct translation from the Chinese):
'Hedwig would attract people's attention... She stands out too much. A snow-white owl that returned repeatedly to the place where he's hiding... What I mean is, owls aren't ordinary local birds, are they?'
This is completely out of line with the facts. Owls of various kinds are actually quite common birds around Britain. How did Hermione make this glaring error?
What Hermione actually said in English was:
'Hedwig'll attract too much attention... She stands out. A snowy owl that keeps returning to where he's hiding... I mean, they're not native birds, are they?'
Hermione originally said that snowy owls are not native birds. A snowy owl is a species of owl, officially known in Chinese as a 雪鴞 xuě-xiāo, quite literally a 'snow owl'. The Chinese translator apparently does not realise this, translating it as 雪白的猫头鹰 xuě-bái de māotóuyīng ('a snow-white owl') or snow-coloured owl.
Having missed the fact that the snowy owl is a particular species of bird, it's easy to mistranslate the rest of the sentence. Instead of saying that the 雪鴞 xuěxiāo is not native to Britain, the translator is on the verge of saying that 猫头鹰 māotóuyīng ('owls') are not native birds. Perhaps sensing that this claim doesn't sit right, she modifies 'native birds' to 'ordinary local birds'.
In any event, the key to the mistake lies in the translator's poor grasp of owl species. For more on this, see The Translation of Owl Species in Harry Potter.