American land-use practices greatly influenced forest composition. The regular use of prescribed fire, the girdling of unwanted trees, and the planting and tending of favored trees suppressed the populations of a number of tree species that did not produce nuts, acorns, or fruit, while increasing the populations of numerous tree species that did. In addition, the burning away of forest-floor litter made these foods easier to find, once they had fallen from the trees. Some have argued that such Native American land-use practices increased the populations of various animal species, including the passenger pigeon, by increasing the food available to them, while elsewhere it has been claimed that, by hunting passenger pigeons and competing with them for some kinds of nuts and acorns, Native Americans suppressed their population size. Genetic research may shed some light on this question. A 2017 study of passenger-pigeon DNA found that the passenger-pigeon population size had been stable for 20,000 years prior to its 19th-century decline and subsequent extinction, while a 2016 study of ancient Native American DNA found that the Native American population went through a period of rapid expansion, increasing 60-fold, starting about 13–16 thousand years ago. If both of these studies are correct, then a great change in the size of the Native American population had no apparent impact on the size of the passenger-pigeon population. This suggests that the net effect of Native American activities on passenger-pigeon population size was neutral. The passenger pigeon played a religious role for some northern Native American tribes. The Wyandot people (or Huron) believed that every twelve years during the Feast of the Dead, the souls of the dead changed into passenger pigeons, which were then hunted and eaten. Before hunting the juvenile pigeons, the Seneca people made an offering of wampum and brooches to the old passenger pigeons; these were placed in a small kettle or other receptacle by a smoky fire. The Ho-Chunk people considered the passenger pigeon to be the bird of the chief, as they were served whenever the chieftain gave a feast. The Seneca people believed that a white pigeon was the chief of the passenger pigeon colony, and that a Council of Birds had decided that the pigeons had to give their bodies to the Seneca because they were the only birds that nested in colonies. The Seneca developed a pigeon dance as a way of showing their gratitude.