an animal builder may collect a variety of materials and use them in complex ways to form useful habitat. the nest of the long-tailed tit, "aegithalos caudatus", is constructed from four materials – lichen, feathers, spider egg cocoons and moss, over 6000 pieces in all for a typical nest. the nest is a flexible sac with a small, round entrance on top, suspended low in a gorse or bramble bush. the structural stability of the nest is provided by a mesh of moss and spider silk. the tiny leaves of the moss act as hooks and the spider silk of egg cocoons provides the loops; thus forming a natural form of velcro. the tit lines the outside with hundreds of flakes of pale lichens – this provides camouflage. inside, it lines the nest with more than 2000 feathers to insulate the nest.