NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: http://mag.outdoornebraska.gov/i/1087556
34 Nebraskaland • March 2019 allowed the shift of cranes from west to east to be quantifi ed in the study, co-authored by Emma Brinley Buckley and others from the U.S. Fish and Wildlife Service, U.S. Geological Service, Rainwater Basin Joint Venture and Platte River Recovery and Implementation Program. The survey area is divided into 11 segments defi ned by highway bridges. Of those, only the four easternmost segments, from Wood River to Chapman, show increasing numbers of cranes. Interestingly, the eastern segment, from Highway 34 to Chapman, hosted so few cranes that it wasn't included in any surveys until the late 1990s. Yet the average count of combined surveys from 2015 to 2017 found 25 percent of all cranes in the central Platte in the two reaches between Grand Island and Chapman. The reach between Alda and Grand Island, where the Crane Trust owns considerable property that has been restored to near-historic form, is the most used segment, boasting a peak density of 6,400 cranes per mile and 32 percent of the count from 2015 to 2017. At the same time, crane use has generally declined in the four segments west of the Highway 10 bridge (Minden), which hosted just 4 percent of the cranes combined. The three segments between Minden and Wood River host 20 percent of the cranes, but numbers in all are also declining, with the exception of the reach from Minden to Gibbon that includes the National Audubon Society's Rowe Sanctuary and a considerable amount of restored land and boasts a stable population. Why Move? With the eastward shift of cranes quantifi ed, the Crane Trust's study hoped to determine why they were moving. Using aerial imagery from 1938, 1998, 2015, and 2016, Caven and his team looked at changes in channel width, and with images from 1998 and 2016, he looked at land cover. "Everyone expected the model to show why wide channels are good and prairie is good," Caven said. "Well, the model showed that prairie was very good, and it also showed wide channels were good. But what's more important than just wide channels is the amount the channel has shrunk since 1938, and that was a more important variable in our model, likely because it's indicative of the change in the character of the river there more than just its width. "That change started in the west and moved east. The perception was that the change has stopped, but that's not the case. We keep seeing more islands popping up in the middle that are becoming stabilized and those are crappy for cranes." The adjacent prairie component of the equation is likely tied to the importance of those habitats, as other studies have found, for the protein provided by macroinvertebrates, for pair bonding activities, and also the cranes' desire to stage next to the river in the evening, continuing forage until dark before returning to roost. Early Arrivals? Research suggests that the greater sandhill crane, which nests primarily in Alaska, Canada and Minnesota, is the fi rst to arrive on the central Platte, and fi lls eastern segments of the river fi rst. The lesser sandhill crane, which nests in Siberia, western-Alaska and northern Sandhill cranes take flight from a cornfield in Hall County. The birds fatten up on crop residue left in the fields, providing energy for the remainder of their migration.