Predator Guard from a Predator

Great crested flycatcher nest with snake skin -  the transient biologist

I have always been amazed how a tiny bird can build a complex nest on a small branch, balancing twigs, grass and even moss until it is firmly woven together.  Francis Skalicky's  article in the News-Leader added a material that was news to me - snake skins!

Tufted titmouse - Joe Motto

Both the Tufted Titmouse and the Blue Grosbeak commonly add bits of snake skin to their nest.  Other species including the Western Kingbird, Bewick's Wren and the House Wren may use snake skin, cellophane, or other flexible plastic as well.  These all would provide flexible, lightweight reinforcement to the twigs.

Research has shown that they may also serve as a predator deterrent as well, similar to a house sign warning that there is a burglar alarm inside. The Tufted Titmouse will incorporate bits of snake skin in its nest while a Great Crested Flycatcher may use a whole snake skin lining the nest with some hanging over the edges to show on the outside.  This flycatcher's eggs are frequently eaten by flying squirrels and rat snakes will take the eggs, the flycatcher and even the flying squirrel that is predating the nest.

So does the snake skin work as a deterrent?  A study described in Birds.com describes the proof.

"A test carried out by the researchers confirmed that to be so. Using 60 nest boxes in which quail eggs were placed, researchers added snake skins into 40 of the boxes, with 20 boxes having no snake skin in them. All of the 40 boxes with snake skins were left untouched, while up to 20 percent of the nests without snake skins were raided by flying squirrels – evidence that some birds use snake skins specifically to ward off predators, and it appears to work." 

If only a Black Rat Snake skin would deter the pack rats in our house!