Happy STS! Thank you for the ask, I'm just getting back on my feet a bit, but I liked this ask so much I had to answer it!
So cursebreakers are both revered and reviled, and when someone chooses to become a cursebreaker they eschew their old life and their old name and they choose an innocuous one. It could be a type of tree, or a rock, or an animal, or a bird, something that doesn't tie them to a place or a family.
Nightjar was born Rura, but chose Nightjar when she became a cursebreaker. She decided that when her daughter was born she wanted to keep her with her, travelling together, no father, no connections, just as anonymous as Nightjar herself, so named her after a little common bird that she often saw on her travels.
Now, she called her wife Siskin as a joke because of the colours she wore when they met, all greens and yellows, and when they adopted their son, Pipit chose to call him Finch, so that he would fit in. It was her way of accepting him into the family, so he was more than happy to go with it.
So really the bird names aren't super important to the worldbuilding, just to Nightjar's little family :)
