In Harry Potter what did ritter skitter turn her self into to spy on hogwarts?

Rita Skeeter didn't turn herself into anything to spy on Hogwarts. She used a magical device called a Quick-Quotes Quill to eavesdrop on conversations and write her sensationalist articles.

The Quick-Quotes Quill was a special quill she got from a goblin. It was a secret, illegal device, and she later got caught using it by Hermione Granger.