Answer by Rory Young:
Yes, they do. Many gregarious and other species of birds will alert each other to anything that looks even vaguely threatening or out-of-place.
Once they learn more about a new creature they encounter, they will begin to relax if they find that it is not interested in them. A good example of how adaptable and able to learn is the Oxpecker. When feeding on ticks on Cape Buffalo they will warn the buffalo of an approaching human. However, Oxpeckers feeding on ticks on cattle will not warn cows of an approaching human.