HR: 08:30h
AN: B51A-01    [Abstracts]
TI: Ecohydrology of Sandhill Crane Riverine Roost Sites
AU: * Kinzel, P J
EM: pjkinzel@usgs.gov
AF: U.S. Geological Survey, Box 25046 DFC M.S. 413, Lakewood, CO 80225 United States
AU: Nelson, J M
EM: jmn@usgs.gov
AF: U.S. Geological Survey, Box 25046 DFC M.S. 413, Lakewood, CO 80225 United States
AU: Heckman, A K
EM: aheckman@usgs.gov
AF: U.S. Geological Survey, Box 25046 DFC M.S. 413, Lakewood, CO 80225 United States
AB: Each spring the Platte River in central Nebraska provides critical nocturnal roosting habitat for approximately 400,000 -500,000 migrating sandhill cranes. Changes in the flow regime of the Platte River over the last century have led to vegetation encroachment and channel narrowing, which has in turn influenced the spatial distribution of crane roost sites. Evaluating the success of management actions such as vegetation clearing or streamflow modification taken to improve habitat for cranes requires an understanding of the physical and biological factors that influence roost site selection. We examined the relationships between flow, geomorphology and roosting habitat for sandhill cranes on the Platte River, Nebraska at two spatial scales. At the sub-reach scale, the locations of roosts are influenced by the flow patterns over and around riverine sandbars. We investigated the relationships at this scale along a 1-km study reach by comparing the pattern of roosts identified with aerial thermal infrared imagery to output from a depth-averaged two-dimensional hydraulic model. Cranes selected roosting habitat characterized by 0.01 - 0.4 m depths and 0.01 - 0.70 m/s velocities. The roost patterns changed with flow, and with the associated distributions of subaerial sandbar area, depth and velocities in the study reach. The amount of roost area in the study reach generally decreased as river flows fell below 23 cubic meters per second and also decreased as flows rose above 48 cubic meters per second. However, for all bed morphologies and river flows modeled the area roosting cranes used was much less than the area available. At the reach scale we examined how the amount of roost area in reaches of different channel type changed for a range of river flows. In the braided channel reaches carrying a portion of the flow, the greatest amount of roost area was observed at the highest river flow. In the single channel reaches carrying the total flow, the greatest amount of roost area was observed at the lowest flow. Taken together these observations may indicate that while cranes show fidelity for certain reaches, there is some threshold at which they abandon these sites in favor of alternate locations that may offer a greater proportion of suitable habitat.
DE: 0400 Biogeosciences
DE: 1800 HYDROLOGY
DE: 1824 Geomorphology (1625)
SC: Biogeosciences [B]
MN: 2005 Joint Assembly