How do young hole-nesting piciform birds defend themselves from danger?

Young hole-nesting piciform birds utilize specific behavioral adaptations to defend themselves from potential threats while inside their nesting cavities. A notable defensive behavior shared among various hole-nesting birds, including members of the order Piciformes, is the production of a snakelike hissing sound when the nest is disturbed.1

This vocalization is thought to serve as a deterrent against predators that might otherwise attempt to enter the nest. Beyond this, the primary protection for these young birds is the concealing nature of the nest cavity itself, which is often excavated in trees, banks, or termite mounds. Because these nests are typically hidden or located within protective substrates, they are inherently more difficult for predators to locate and access compared to exposed nests.2