The Ornate Hawk-eagle, a bird found in Tropical South America, is a stealthy eagle that hunts prey from treetops. It is usually found in warm climate, which the birds thrive in. However, 30 to 20 millions years ago, the tropics extended further north than usual, reaching the United States. This climate change helped the Ornate Hawk-eagle spread further north, possibly as far as Nebraska.

When the climate changed again and began to cool down, Hawk-eagles began to decline in the United States and moved on to South America, so today, we do not see Hawk-eagles in Nebraska.

The fact giant eagles lived in North America is amazing, and North America at that time was home to many different kinds of mammals, the new masters of the Earth ever since 40 million years ago. Daedon, nicknamed the killer pig, was the top predator at that time in North America. Certain South American birds of 1 million year ago, like Argentavis, a giant bird that hunted small horses. It hunted them possibly by landing on them and killing them with a heavy blow. Perhaps  Hawk-eagles in Nebraska possibly hunted the same, except with smaller prey.