2:00PM, OCTOBER 8, 2014
Bird’s nests come in a wide variety of shapes and sizes, and they’re built out of all sorts of things. Hummingbirds, for instance, create tiny cups just a couple centimeters wide; sociable weavers in Africa, in contrast, work together to build huge nests more than two meters across that are so heavy they can collapse trees. There are nests built on rocky ledges, in mounds on the ground, high in trees and on the edges of buildings. Bowerbirds even construct their nests as tiny houses decorated with an artistic eye to attract the ladies.
So perhaps it’s not all that surprising the no one had ever investigated whether birds camouflage their nests to protect their eggs against potential predators. It would make sense that they do, but if you were to test it, where would you start?
For Ida Bailey of the University of St. Andrews in Fife, Scotland, and colleagues, the answer was zebra finches. Male finches usually build nests in dense shrubs and layer the outside of the nests with dry grass stems and fine twigs. Predators, usually birds, take a heavy toll on the zebra finches, though. Since birds tend to hunt based on sight rather than smell, camouflaging a nest might work to protect the eggs sequestered inside. And even better, because zebra finches have good color vision, building a camouflaged nest might be possible.