FWS Region 3 Aviation Program, FWS Division of Migratory Bird Management, FWS National Aviation Management Branch, U.S. Geological Survey (USGS) Geomorphology and Sediment Transport Laboratory, USGS Upper Midwest Environmental Science Center
Every spring, over a half-million sandhill cranes converge on Nebraska’s Platte River valley during their annual migration northward to Arctic and subarctic nesting grounds. This gathering represents a majority of the world’s sandhill cranes, and thus presents a unique opportunity to document and monitor their population status. In late March, the FWS routinely conducts a low-level aerial survey of the cranes using visual estimation techniques. One drawback of this methodology is that the widely dispersed foraging behavior of the birds during the daytime, when the aerial flights occur, can yield highly variable counts.
In keeping with its long tradition of promoting remote sensing innovation, the FWS Region 3 Aviation Program has coordinated with internal (FWS Division of Migratory Bird Management and National Aviation Management Branch) and external (USGS Geomorphology and Sediment Transport Laboratory and USGS Upper Midwest Environmental Science Center) partners to incorporate a FLIR SC8340 thermal infrared camera into a direct-georeferencing aerial imaging system aboard the survey aircraft. The camera allows surveys to be conducted at night, when the cranes have concentrated on the river to roost and their thermal signature shows up distinctly against the colder surroundings; the direct-georeferencing capability enables pinpoint location accuracy, even at higher flying altitudes. A pilot study conducted during the springtime 2016 population survey produced encouraging results: the acquired thermal data allowed the detection of individual birds, and the rapid orthocorrection and production of imagery mosaics facilitated the accurate estimation of overall population numbers.
The production of orthocorrected imagery and prospects for a long-term imagery archive will assist in ongoing critical habitat monitoring and restoration efforts on the Platte River for cranes, waterfowl, and other wildlife species. The integration of the FLIR system will ultimately support wildlife population monitoring objectives where individuals may be hard to detect visually, and furthers the FWS goal of increasing aviation safety by reducing the risks associated with low-level visual aerial surveys.
(L) A high-resolution satellite image shows a sandhill crane roosting area on the Platte River in April 2006. (R) A thermal image overlaid on Google Earth imagery illustrates the accuracy of the georeferencing and the differences in the birds’ thermal signatures from their surroundings: the water appears light, with areas of birds appearing gray and textured. The imagery was collected at a safe flying altitude of 2,000 feet above ground level.