Close observation of over 140 birds’ nests reported the presence of snakeskin as part of the material used in construction of the nest. This is a practice used by some 78 different species. A new study in the American Naturalist questioned what the reason for this phenomenon is. Snakes shed their skins as they outgrow them in one piece as opposed to other reptiles that shed them in patches. These skins are difficult to locate in the wild which makes it even more intriguing on how these birds secure them. In studying the behavior of nesting birds, it was discovered that this practice of incorporating snakeskin into the nest was used primarily by birds along cliffs or in rock cavities. Snakeskin seems to deter small animals or any type of predator from invading a nest where they feel there is the presence of a snake. Other research in Australia is showing that some birds will even start to hiss as they perceive some type of danger may be approaching the nest.
https://www.audubon.org/news/some-birds-adorn-their-nests-snakeskin-scare-predators-new-study-finds