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Table 1 Sampling variables for the selection of foraging habitats

From: Foraging habitat selection of overwintering Black-necked Cranes in the farming area surrounding the Caohai Wetland, Guizhou Province, China

Category Variables Description
Topographic factorsSlope degree (°)Large quadrat: < 10° = 1, 10°‒20° = 2, 20°‒30° = 3, > 30° = 4
Slope aspectLarge quadrat: shady slope = 1 (‒67.5° to 67.5°), sunny slope = 2 (112.5°‒247.5°), semi-sunny slope = 3 (67.5°‒112.5°, 247.5°‒292.5°)
Slope positionLarge quadrat: upper = 1, middle = 2, lower = 3
Human disturbance factorsDistance to water (m)Straight-line distance (m) between the center of a large quadrat and the nearest water (ditch, canal, brook, or pool)
Distance to settlement (m)Straight-line distance (m) between the center of a large quadrat and the nearest residence
Distance to road (m)Straight-line distance (m) between the center of a large quadrat and a road
Distance to tillagers (m)Straight-line distance (m) between the center of a large quadrat and the nearest farmer working at a site
Food factorsTypes of food Type of crop: corn, potato, radish, cabbage, rape, shallot, green manure, tobacco
Food richnessIf more than two kinds of crops were in a large quadrat: yes = 1, no = 0
Crop remains (g/m2)The crop remains (g/m2): the average of 5 small quadrats, measured by an electronic balance
Tillage methodsWhether the crop patch was plowed by machine: yes = 1, no = 0