Sandhill crane migration under way, passing through Illinois
Autumn has hit: spectacular sandhill crane flocks have begun migrating.
Thursday, October 13, 2011 - 13:55
CURIOUS & ALERT: Sandhill cranes drawn to something nearby. (Photo: Stepan Mazurov/Flickr)
We are now fully in the throes of autumn, and that means many migrations have begun. One of the most spectacular migrations is that of the sandhill cranes, who migrate from the far north of the northern hemisphere to the far south. The flocks often number in the thousands, and they have several spots along the way where they roost in incredibly large groups. In Illinois, one is more likely to see one of their flocks traveling, but it is still a spectacular sight.
They have a distinctive sound, and if you are searching for cranes, you'll likely hear them before you see them. You can listen to a sample from Wikimedia Commons of what they sound like here. Their calls are relatively loud, so you might even hear a flock of cranes without seeing them. It's hard to distinguish them from flocks of geese without the sound, since they fly so high up and in such big numbers.
When they do land for the night, they tend to land in very large fields due to their large numbers. This can be a problem, since they tend to disrupt agricultural fields, creating a problem with farmers. It's likely that before most wild land was domesticated, the sandhill cranes landed in prairie areas.
Sandhills are some of the only birds, other than raptors, that can soar. Since they have a very large wingspan (around six to eight feet across), they ride on thermals (pillars of warm air), and can often soar for hours. They use minimal amounts of energy that way, so that is why they are able to migrate that far. When they land in the fields, it's interesting to watch their behavior. Mated pairs often do something called "unison calling," in that they call at each other in a way that weaves together, forming a duet. They also dance at each other, jumping up and down and moving their wings in a sort of display.
Sandhill cranes are also a very old species, in terms of evolution. The oldest sandhill fossils that have been found are around two and a half million years old. There is also a ten-million-year-old fossil that may or may not be of this species — but even the two-and-a-half-million-year-old fossil is far older than most bird fossils. These magnificent birds are probably nearer to when birds began to diverge from reptiles than the majority of bird species.
Seen any near you?
Photo: Stepan Mazurov/Flickr