Mud and the Evolution of Land Animals

Mud is also a nest building ingredient. Various birds collect mud in addition to other elements to build their nest. Using mud is kind of a glue or mortar. Swallows are the best example of mud use in birds, but various birds use mud to some degree. But still, if you haven't seen a swallow nest, you should look at one. This is not the bird nest that your kindergarten teacher kept in a shoebox to show you. No, this one looks like a real disaster if it gets wet.