Construction of models to predict the breeding density of carrion and jungle crows (Corvus corone and C. macrorhynchos)
2006
Momose, H.(National Agricultural Research Center, Tsukuba, Ibaraki (Japan)) | Yoshida, H. | Yamaguchi, Y.
Nesting locations of two species of crows, the Carrion crow Corvus corone and the Jungle crow C. macrorhynchos, were studied in five areas of total 58 km(2) near Tsukuba city in southern Ibaraki prefecture, about 50km northeast of Tokyo. Using these data, multiple regression models were constructed to predict the breeding density (number of nesting locations within a lxl km or 2x2 km grid) of the crows from environmental factors such as vegetation, land use and terrain structure. Overall, 2x2 km grid models were better than lxl models and the one to predict the breeding density of the two crow species combined was better than separate models. The factors used in this "combined" model were the total length of the forest edge facing farmland, paddy field, orchard, grassland and urban area and the area of farmland (R(2)=0.83). The presence of these edges might indicate the abundance and the proximity of foraging and nesting habitat for the crows. The model to predict the ratio of the two species was also constructed (R(2)=0.77). Its structure suggested that forested areas tended to have more Jungle than Carrion crow nests.
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