They exposed a crew of western scrub jays to three piece of stimuli — a stuffed and mounted dead jay, a stuffed and mounted great horned owl, and a neutral item. The neutral item being just a bunch of sticks that kind of looked like you could mistake them for a dead bird if you were standing far away.
The birds were like, hey those sticks are just sticks. But when they saw the owl they freaked out and squawked 80 per cent of the time and they had the same reaction with similar frequency when they saw the jay. They also foraged less when they saw these taxidermied dummies.
Conclusion: birds may be dumb, but at least they have enough common sense and see bird carcasses as indicative of incoming danger, so they gather and flip out in an effort to protect the nest from predators. Honestly, birds are awful creatures. [Ars Technica]