Interrupt this programming for a comment on the hummingbird egg.... Birdlady_Susie says:
"I would agree on the new egg might not thrive, even if it were to hatch from being sat on by the new babies and the mom. It will help hold heat in the nest, I have Lady Gouldian finches that have done this and successfully raised the last baby, even though it was sooo much smaller than the others. In some birds, the urge to be successful in raising young is very strong. Of course in raptors, the bigger babies will usually kill any late hatch babies, food competition is so strong. One just never knows what can or will happen."
Susie would love an update on the egg should something happen. Of course, something WILL happen, just what will be the surprise!