Squirrel VS Cobra!

http://www.thesun.co.uk/sol/homepage/news/3811857/Brave-squirrel-scoffs-at-snake.html

I post this article for two reasons.  First of all, it's kind of interesting, even cute.  But secondly, please check out the seventh mini-paragraph.  Can you tell me what this sentence means:

"Sightings like this are rare – but they are not uncommon."

Any ideas?