Cat Imitates Bird Sounds to Trick Magpie

Gypsy the cat is a mimic. She 'talks' to birds, lulling them into believing she's a bird too. I have never heard a cat do this before but it is not uncommon. Gypsy was purchased at 12 weeks so this trick of hers could not have been learnt from her mother, it must be instinctive. But then I wonder why all cats don't do it!