Habitat selection by Secretarybirds observed in the Coordinated Avifaunal Roadcounts (CAR) project in the 16 precincts for which there were sufficient data, in summer (S) and winter (W) counts.

Jacobs index D values indicate selection for natural habitats if positive, and for transformed land if negative. The Natural and Transformed columns give the numbers of routes on which Secretarybirds showed a preference for natural or transformed habitats respectively. Sign test p values refer to tests of whether the number of routes with positive or negative Jacobs index D values was significantly different from that expected if zero selection had been shown.雅各布斯D指数（Jacobs index D）的取值若为正，代表对自然生境的选择偏好；若为负，则代表对人工改造生境的选择偏好。"自然"与"人工改造"两列分别统计了蛇鹫（Secretarybird）对自然生境或人工改造生境表现出偏好的样带数量。符号检验（sign test）的p值用于检验：雅各布斯D指数为正或负的样带数量，与无选择偏好（即选择强度为0）时的预期数量是否存在显著差异。