Up close with cranes
By NET News
March 24th, 2014
Omaha, NE — Much of the ground was still frozen on a recent March afternoon on Mormon Island in central Nebraska. This “island” runs for several miles between two channels of the Platte River. Mary Harner, director of science at the Crane Trust, leads the way to a wet meadow: low-lying, undulating grasslands near the Platte, carved by older flows of the river.[audio:https://kvnonews.com/wp-content/uploads/2014/03/gettingupclosewithcranes3_20_14KVNO011.mp3]
Standing on an ice-covered portion of the slough roughly 20 feet across, Harner explained once the ice melts, this area will have flowing water. These aptly-named wet meadows are closely connected to the groundwater just below the surface, and usually marsh-like in spring and summer. Their moist soil makes it easier for birds to find bugs and plants to eat.
Last spring, Harner and other researchers set up 10 game cameras over multiple sites in the meadow. The small, camouflaged cameras were set up to take pictures every half hour or when they detected motion.
“We had cameras paired between the low wet areas and the nearby drier areas going from south to north across this island,” Harner said.
More than half a million sandhill cranes depend upon this shallow river, its sandbars and nearby wetlands to rest and feed on during their annual spring migration, Harner said. But much of their critical habitat has disappeared. The Crane Trust is one of several organizations working on conserving what remains along the central Platte, using methods that mimic historic forces on this river habitat — like fire and grazing.
“These wet meadow habitats are very rare. They’re one of the first habitats to be lost when river flows are diminished and floodplains are converted from their natural state. So we’re here to first and foremost protect the remaining grasslands and meadows like this,” Harner said.
Harner and her colleagues think these cameras might help them learn more about how and why the birds use these areas, which will help their conservation work.
Paul Johnsgard, a renowned ornithologist and retired biology professor at the University of Nebraska-Lincoln, has spent his career studying cranes and other birds.
“Spring biology of cranes is really important because these six weeks or so that the birds spend in the Platte Valley are critically important for them to acquire the amount of fat, energy, that the need for the rest of their spring and summer activities. So it really is important to get this kind of data,” Johnsgard said.
Crane video cameras have been around for a while, but most of the information about cranes has come from aerial surveys, thermal imaging, and people watching from wildlife blinds. Using the cameras to get thousands of up-close images offers a different way to study sandhill crane biology.
“You get an enormous sample of thousands of data points and from that you can look at them statistically and figure out exactly what percentage of time birds are doing different things. It gives a set of real data instead of general perceptions,” Johnsgard said.
That data would be almost impossible to get without human presence affecting crane behavior, according to Greg Wright, wildlife biologist at the Crane Trust. Part of the initial study involved figuring out where to put the cameras, said Wright, “We didn’t know exactly how they would respond to these cameras being out there. The camera is small and fairly discreet, and it’s camouflaged but still, in a grassland, anything sticks out.”
Wright said their time-lapse photography approach builds on previous wildlife studies, and cranes make an ideal subject for this kind of technology because of their “fidelity” to the Platte River, where they’ve returned year after year, for centuries.
“The nature of cameras, when you can’t move them, you need a bird that has some sort of fidelity to a site. Other than nests there’s not too many places that birds return to again and again in a way that you’d have enough images to be able to discover a pattern. Cranes fit that bill,” Wright said.
The idea for the study came from an existing partnership with the University of Nebraska’s and NET Television’s Platte Basin Timelapse project, which has been collecting time-lapse images across the river system for the past three years.
Harner said changing technology has recently made these kinds of studies much cheaper and easier for researchers. Photos and videos are also more accessible for the general public than papers or graphs, Harner said, “being able to show how the groundwater is pulsing and how these grasslands are essentially breathing … it just brings it to life in ways that are nearly impossible to visualize otherwise.”
Student interns helped classify more than 67,000 unique behaviors from tens of thousands of images collected last March and April. Wright said their initial findings show cranes tend to congregate in the wetter parts of the meadows, where they did more bathing and resting, compared to drier upland areas, where they mostly ate and moved around.
“I think we were surprised that there were these strong differences between the uplands and the sloughs — the water areas,” Wright said.
Camera data also offered rare glimpses of birds spending the night in the meadows, rather than returning to the river as they normally do. This spring the Crane Trust will use the cameras to study nighttime behavior of cranes on the river, Wright said.
“We don’t know what the birds are necessarily doing. We know they stay on the river. But to be able to have a camera right there on the roost and see those birds throughout the night … We’ll be able to see their activity pattern through the night,” Wright said.
The project should help researchers and the public alike learn more about Nebraska’s annual winged travelers.
Comments are closed.