I read this paperback in the 60s, probably published in the 50s or earlier, set in the UK. The dark-haired heroine, Petrova (?), was a second child. She loved seeing wild birds, wonderful descriptions eg a flock coming in over an estuary.
Stump the Bookseller
New format, same book stumper solving.
Petrova is the middle sister in Noel Streatfeild’s ‘Ballet Shoes’ – the non-dancer/actress one who wants to be an aviator when she grows up. It’s been many years since I read it and I don’t remember the descriptions of the birds but it’s such an unusual name, this must be it.