And she reads -- for utterly unrelated reasons, because it's about the exotic wonders brought to China during the T'ang dynasty -- a book that makes mention of the Chinese "Roving Women Who Go By Night" also known as the "Daughters of the God-King of Heaven" or the "Star Anglers" who can take off feathers and put them to shift from woman to bird.
They also have no children and steal other people's. This is why you should not give children candy in exposed places. Also, do not expose the children's clothes to sunlight; if a feather from these women's plumage falls on it, there's danger of a bird-demon. The women fly about by night rather than day. Some people claim they are the ghosts of women who died in childbirth. . . hmm, one suspects a degree of propitiation in the second name.
So in this world of innocuous and imperiled bird-women -- is this just a silly story? Are there actually malicious bird-women like that? (There are, after all, malicious werewolves and wizards and dragons and many other evil types.) Or is it a warped view of families whose children escaped through a combination of being a descendant of a bird-woman, being miserable in their lives and suited to be a bird-woman (or sometimes bird-man), and finding a feathered-cloak? It's easy to regard your children as stolen even when the flight was wholly voluntary.
(And thus showing the advantages of reading widely even in history books that do not appear to be related to the subject you are interesting -- now, where did this soapbox come from? and why am I standing on it?)