[Ditter]

I just had another thought about this. Like the chickens being hypnotized by a string, maybe it was the same thing when they looked up and saw the big rain drops coming down on them. They were hypnotized and couldn't stop looking up.

[Yardstick]

Okay, that does seem like a plausible explanation. The chicken goes into a hypnotic state and freezes in place, allowing the rain water to run down into its lungs. It only takes a few teaspoons of water to drown a person so probably much less for a chicken. I think you might be on to something here.