The most popular gathering space in the Chicago area is at Indiana's Jasper-Pulaski Fish & Wildlife Refuge, where they congregate directly in front of the Sandhill Crane Observation Deck.
"Most of these birds will probably (end up) in Florida," said Nat Miller, executive director for Audubon Great Lakes.
"But more and more, climate change is probably contributing to this, some of these birds are over-wintering in the Midwest. So you'll even have some birds stay here for the winter if they can make do."
Sandhill Cranes are what Miller calls a "conservation success story" amidst a string of wildlife losses in the western hemisphere. A recent report from Science magazine cited the loss of three billion birds since 1970, accounting for one quarter of the west's birds.
Conservation science manager Stephanie Beilke said wetlands conservation has played a major role in the health of Sandhill Cranes.
"Across most of their populations, they're doing very well. That hasn't historically been the case," Beilke said. "I believe in Wisconsin, they had only a few dozen pairs left at one point. So there was a reintroduction process, and we've seen them rebound."
To see the cranes on their migration, visit Jasper-Pulaski before the end of December.
"These birds have been around for two million years," Miller said. "It's special, and I think you feel that when you're here with them."