How do pigeon squabs defend themselves when a predator approaches the nest?

When a predator approaches the nest, pigeon squabs utilize a specific threat display to defend themselves. They inflate their crops with air to appear significantly larger and thrust their heads toward the intruder while hissing and snapping their mandibles together.1

This behavior is an effective antipredatory measure, as unguarded squabs are less vulnerable to predation than eggs, partly due to this display and their cryptic coloration.1