A pair of bluebirds raised a second brood in my birdhouse and I was glad to see them leave what I am sure was an unbearably hot nest (105 degrees here in MD today). One bird of the four has not made an attempt to fly away and the mother is nowhere to be seen. I am afraid that it has been abandoned. Could it be not developed enough to fly and will starve without care from the mother. I assume there is nothing I can do and will just have to let nature take its course.