A banyan is a fig that starts its life as an epiphyte when its seeds germinate in the cracks and crevices on a host tree (or on structures like buildings and bridges). "Banyan" often refers specifically to the species Ficus benghalensis, though the term has been generalized to include all figs that share a unique life cycle, and systematically to refer to the subgenus Urostigma. The seeds of banyans are dispersed by fruit-eating birds. The seeds germinate and send down roots towards the ground, and may envelope part of the host tree or building structure with their roots, giving them the casual name of "strangler fig." The "strangling" growth habit is found in a number of tropical forest species, particularly of the genus Ficus, that compete for light. Any Ficus species showing this habit may be termed a strangler fig.