Bird nests come in all shapes and sizes, crafted from a diversity of materials, including fur, grasses, leaves, mosses, sticks and twigs, bones, wool, mud and spider silk. Quite a few contain man-made materials ? twine, bits of wire, even plastic bags. Each is a work of art, built with just a beak! All over the world, birds in the wild arrive at diverse nesting grounds to collect, compete for, reject, steal and begin to build with carefully selected materials, crafting homes for the task of protecting their eggs and raising their young.