Originally Posted by
Rock Monkey
So sorry to hear this.
The good thing about a drey is that it is a ball, sort of, a flexible ball, various sticks and leaves woven together. So hopefully this means that it wasn't a hard impact, it might have bounced off a few branches on the way down, absorbing some energy and preventing it from gaining too much speed.
If a baby were dead I don't think she would leave it in the box. Your nose will tell you soon enough. Hopefully she will have transferred all of the babies over.
They do sell endoscope cameras on Amazon which can be hooked to your cell phone. This would allow you to look in the nest box, but Mom may not be happy about the intrusion. They don't cost too much.
You might try putting a zip lock filled with water near the entrance. Supposedly, this inhibits flies, the water in the bag. I have never tried it, so I don't know if it actually works. But it is low-tech and simple and I don't think it could hurt to try.