The Midcontinent Population (MCP) of Sandhill Cranes (Grus canadensis, herein; cranes) is the largest population of cranes in the world, and is recognized as a surrogate species for the ecological functions of broad landscapes in the Southern High Plains (SHP) of western Texas. We hypothesized that crane resource selection patterns in this region may change across late fall, winter, and early spring as a function of changes in the temporal distribution of available playa lakes and other waterbodies, and the temporal dynamics of grain crops. Cranes (N=17) were trapped, banded, and tagged with platform transmitter terminal GPS devices during the winter of 2014-15. Waterbodies were delineated through random forests supervised classification of 2014-15 Landsat 8 imagery using the Google Earth Engine platform. We used a grid with cell sizes of 2.5 x 2.5 km to calculate the difference in waterbodies surface area mapped from summer to winter in 2014 in each cell (“SWDIFF”) and used crane GPS locations to evaluate whether crane resource selection was determined by increasing or decreasing water availability from summer to winter. The selection of crops by cranes was quantified by calculating the Manly selectivity index during the winter using the 2014 USDA CropScape dataset.
Results/Conclusions
Cranes significantly selected for high-yield agricultural cropland and open water during the winter of 2014-15, showing strong Manly selectivity measures and selection ratios for these land cover classes. Increasing selection ratios were found for corn from the first (wF= 0.00, BF= 0.00) to the last month (wL= 30.34, BL= 0.08), but decreasing selection ratios were found for cotton from the first (wF= 62.87, BF= 0.17) to the last month (wL= 29.52, BL= 0.08). Different selection ratios were found in the first month, middle phase, and last month of the overwintering period for open water (wF= 99.47, BF= 0.27; wM= 65.58, BM= 0.135;wL= 106.72, BL= 0.27) and herbaceous vegetation (wF= 132.64, BF= 0.36; wM= 274.48, BM= 0.57; wL= 173.01, BL= 0.44). There was a significant difference between SWDIFF in areas used by cranes (x̄=22,755.44, SD=146,628.06) and areas unused by cranes (x̄=-11,031.04, SD= 100,718.57; t[139]=2.297, α=0.05). Results suggest that cranes prefer areas with stable or increasing water resources during the overwintering period and that crop type and productivity dynamics can influence crane resource selection. Future research will analyze the role of different types of waterbodies and primary productivity dynamics in crops and their influence on crane resource selection during the overwintering period.