Thunderbirds are powerful spirits found throughout most of North America. Accounts of these beings vary depending on the people who tell of them; sometimes the thunderbird is a singular being while other times it is a species. It may be dangerous or helpful. Sometimes it can take on human form by removing its beak like a mask and live among humans for a spell, even becoming ancestors to a group of people. But there are common traits of the thunderbird. Similar in shape to the eagle, the beating of its wings creates the rolling thunder and pulls the clouds together. Lightning flashes from its eyes or beak. And these thunderbirds could influence or control the rains.