Sandhill cranes are regular visitors along the Platte River. During the spring, more than half a million cranes stage there from mid-February through early April. Once they build up sufficient fat reserves they continue north to breed in Minnesota and Canada.
They appear again in the fall, but normally just for a quick visit as they hurry south toward their wintering grounds. Usually, they are more heard than they are seen, as they glide far overhead. A relative few stop and roost on the river for a night or so, and those overnight guests might do a little feeding in the recently harvested corn fields or meadows. Unless the weather keeps them longer, though, they usually arrive one evening and leave the next morning.
This year, however, something's different. Chris Helzer, Eastern Nebraska Program Director, reported on December 19th that, “There are thousands of sandhill cranes roosting and feeding along the river - and they've been here for more than two months. For the first several weeks, we assumed it was an anomaly, and that they'd be moving on soon. Now we're starting to wonder if they're planning to stay all winter!”
The unexpected congregation of cranes is causing considerable discussion and speculation among biologists. No one can remember this happening before, so why this year? Is it related to the severe drought in Texas and other places in the south where the cranes typically spend their winter? If so, did the cranes go down, look around, and turn back north?
“For a while, we figured it was just the mild November temperatures and strong river flows that were keeping them here. If it's not cold and snowy, why leave?” said Helzer. “Since then, we've had some very cold (albeit short) snaps and two substantial snowstorms come through. And they're still here.”
Helzer emailed Dave Brandt, with the U.S. Geological Survey's Northern Prairie Wildlife Research Center to get his input on the discussion. Dave is part of a team (along with Gary Krapu) that has been doing a lot of telemetry work on the mid-continent sandhill crane population, and tracking where they go. He said that "reflux migration" (cranes bouncing back in the direction they came from) because of severe weather conditions is not unheard of, but is very rare. They're not following cranes intensively now, but he did say that there were 16 marked birds they'd been watching, and that all had migrated all the way south.
Brandt was actually in Texas when he emailed, and said there were sandhill cranes there, but that it was very dry. His best guess was that "our cranes" were just taking their time coming south because of the nice weather. That made sense to Helzer. However, that was a month ago, and before the cold and snowy weather hit!
“This is one of those phenomena that makes it great to be a biologist,” said Helzer. “You think you've got a species really figured out, with strong patterns of behavior that repeat time after time - sandhill cranes have been very well studied - and then the species throws you a curve ball.”