flowering plants provide a variety of resources – twigs, leaves, petioles, roots, flowers and seeds. basal plants, such as lichens, mosses and ferns also find use in structures built by animals. the leaves of grasses and palms being elongate and parallel-veined are very commonly used for building. these, along-with palm fibers and horse-hair fern are used to build hanging baskets. wooden twigs form the greater proportion of materials used in the nests of large birds. plants and trees not only provide resources but also sites. branches provide support in the form of cantilevered beams while leaves and green twigs provide flexible but strong supports.