this is clearly a bloke pretending to be JKR for laughs. I’m quite young but from my experience only British men in their 40-50s use the term “ bird” to mean woman. I’ve not met any women who uses that term even amongst women in their 40-50s lol .

It's also a very poor quality photoshop. First thing that jumps out is that there is too much white space between @jk_rowling and the text and after the text.

A quick investigation find this which appears to be the original tweet: https://twitter.com/jk_rowling/status/1541044356932583424

They cut the text and put in the above but had to hide that there were 3 more lines of text in the original with their dodgy photoshop skills.