I was thinking... I dunno, Moonfleet, The Moondial, Tom's Midnight Garden etc other books I read from when I was a child.
I don't want to worry you, but we're all about to die:
Dunnocks are known for their active breeding habits that differ very much from other birds. Female Dunnocks sometimes have multiple partners in hope that they’ll both help to take care of her chicks. However, males have become wise to this and are known to peck at the female’s cloaca to encourage her to reject the sperm.