On J.K. Rowling's old website there is an "Extra Stuff" post that reads as follows
Owls feature in many superstitions across the world. To the Greeks, the owl was emblematic of Athena, goddess of wisdom and war, and if an owl was sighted flying over the Greek army prior to battle it was considered an omen of victory. To the Romans, on the other hand, the owl was an unlucky creature that predicted death and disaster. In Britain there is a superstition that it is unlucky to see an owl by daylight, a superstition I had fun with in the first chapter of ‘Philosopher’s Stone’ where, of course, the sudden explosion of owls flying by daylight represented something very lucky indeed, though the Muggles did not know it.
My wizards' owls reflect their personality to a certain extent. Poor Ron gets Pigwidgeon, who is a Scops (these are very small owls with ears – cute, but distinctly unshowy). Poor exhausted Errol is a Great Gray, which in my opinion is the most comical-looking owl in the world – just Google the Great Gray to see what I mean. Naturally I gave my hero what I consider to be the most beautiful owl of the lot: the Snowy Owl, which also goes by the name of Ghost Owl. These are not native to Britain, so I felt that she would give Harry kudos at Hogwarts (there is no other snowy owl there, as I trust you have noticed). However, any owl expert would tell you that Hedwig is strangely atypical of her breed. Only after Philosopher’s Stone had been accepted for publication did I realise that Snowy Owls are diurnal. I think it was during the writing of ‘Chamber of Secrets’ that I discovered that Snowy Owls are also virtually silent, the females being even quieter than the males. So all of Hedwig's night-time jaunts and her many reproving hoots may be taken as signs of her great magical ability or my pitiful lack of research, whichever you prefer.
(Incidentally: there has been a spate of stories in the press recently concerning the upswing in popularity of keeping owls as pets, allegedly as a result of the Harry Potter books. If it is true that anybody has been influenced by my books to think that 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: please don’t.)
Looking through old forums shows that this post was replacing a previous post and provides some dating. It seems that the original was posted on January 31st 2005 and that it was replaced the next day on February 1st 2005.
I have been unable to locate the original version in full, but I have found two quotations from it.
If it is true that anybody has been influenced by my books to think that an owl would be happiest shut in a small cage and kept in a house, I would to take this opportunity to say as forcefully as I can: YOU ARE WRONG.
The owls in the Harry Potter books, which deliver the mail by magical means, were never intended to portray the true behaviour or preferences of real owls. If your owl-mania seeks concrete expression, why not sponsor an owl at a bird sanctuary where you can visit your owl and know that you have secured him or her a happy, healthy life?
It is worth noting that it seems like the original post was only about not keeping owls as pets, and so if it was longer, it probably wasn't more than a sentence or two longer.
What was the exact text of J.K. Rowling's original post on her website?
This has been bothering me for some time, so I'll gladly award a 300 bounty to anyone who can provide the full text with sufficient proof. (e.g. A contemporary source that presents the original writing in its entirety as a single block quote)