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From late February to early April the Central Platte River Valley in Nebraska is home to the largest gathering of Sandhill Cranes (Antigone canadensis) in the world and increasingly serves as a foraging ground for migrating Bald Eagles (Haliaeetus leucocephalus). On 7 March 2017, we documented a subadult Bald Eagle depredating an adult Sandhill Crane. Though evidence suggests that Bald Eagles depredate Sandhill Cranes on rare occasion, the process of that depredation has not been described in the scientific literature. The Sandhill Crane effectively defended itself several times against hovering attacks from the Bald Eagle by utilizing wing-spread displays and “bill stab” attacks. However, the Bald Eagle was eventually able to land on the Sandhill Crane's neck and back with its talons, push the crane's head under water, and drown its prey. Following submersion, the Sandhill Crane was only momentarily responsive before floating on its back down the river. We also documented 5 subadult Bald Eagles competing for access to a second Sandhill Crane carcass. As Bald Eagle populations continue to recover, Sandhill Cranes may become more frequently depredated by Bald Eagles during the spring migration-staging period in the Central Platte River Valley.

Over 80% of the Mid-Continent Sandhill Crane (Antigone canadensis) Population (MCP), estimated at over 660,000 individuals, stops in the Central Platte River Valley (CPRV) during spring migration from mid-February through mid-April. Research suggests that the MCP may be shifting its distribution spatially and temporally within the CPRV. From 2002 to 2017, we conducted weekly aerial surveys of Sandhill Cranes staging in the CPRV to examine temporal and spatial trends in their abundance and distribution. Then, we used winter temperature and drought severity measures from key wintering and early migratory stopover locations to assess the impacts of weather patterns on annual migration chronology in the CPRV. We also evaluated channel width and land cover characteristics using aerial imagery from 1938, 1998, and 2016 to assess the relationship between habitat change and the spatial distribution of the MCP in the CPRV. We used generalized linear models, cumulative link models, and Akaike's information criterion corrected for small sample sizes (AICc) to compare temporal and spatial models. Temperatures and drought conditions at wintering and migration locations that are heavily used by Greater Sandhill Cranes (A. c. tabida) best predicted migration chronology of the MCP to the CPRV. The spatial distribution of roosting Sandhill Cranes from 2015 to 2017 was best predicted by the proportion of width reduction in the main channel since 1938 (rather than its width in 2016) and the proportion of land cover as prairie-meadow habitat within 800 m of the Platte River. Our data suggest that Sandhill Cranes advanced their migration by an average of just over 1 day per year from 2002 to 2017, and that they continued to shift eastward, concentrating at eastern reaches of the CPRV. Climate change, land use change, and habitat loss have all likely contributed to Sandhill Cranes coming earlier and staying longer in fewer reaches of the CPRV, increasing their site use intensity. These historically unprecedented densities may present a disease risk to Sandhill Cranes and other waterbirds, including Whooping Cranes (Grus americana). Our models suggest that conservation actions may be maintaining Sandhill Crane densities in areas that would otherwise be declining in use. We suggest that management actions intended to mitigate trends in the distribution of Sandhill Cranes, including wet meadow restoration, may similarly benefit prairie- and braided river–endemic species of concern.