Hi William that's a long time when it says on the BTO website incubation is 13-15 days, but I wonder if they only start full incubation when she's laid all the eggs.
Thanks for replying Alan. They were all laid about 27 days ago. How long do u think she will sit before giving up?
No way of knowing how long before she twigs. Sounds like eggs are infertile to me though.