2015 Volume 64 Issue 2 Pages 207-218
Three species of crows, Carrion Crow Corvus corone, Large-billed Crow C. macrorhynchos and Rook C. frugilegus (a migratory winter visitor) often roost together in Shonai, Yamagata Prefecture, Japan. In order to help understand how these closely related crow species are able to live together in the same locality, we investigated their food habits by DNA analysis of their pellets. Pellets were collected from beneath roosts for analysis of their DNA and species contents. The percentages of three food groups: (a) invertebrates, (b) plants and (c) ‘others’ found in pellets were as follows: Carrion Crow (a) 77.1, (b) 82.1, (c) 10.6; Large-billed Crow (a) 43.9, (b) 73.8, (c) 47.2, and Rook (a) 17.1, (b) 97.6, (c) 0. Carrion Crow pellets contained such organisms as ground wandering arthropods, herbaceous plant fruit seeds, and small herbivorous insects inhabiting paddy fields or wetland edges. These organisms typically occur close to the ground surface. Organisms inhabiting paddy fields were detected in Carrion Crow pellets throughout the year. In addition, they included items such as fruit seeds and insects that occur in tree crowns. In contrast, Large-billed Crow pellets were found to contain items typically found in trees, urban areas and garbage, whereas Rook pellets included mainly residual post-harvest rice grains derived from paddy fields. We conclude that although the diets of these three crow species overlap partially, Carrion and Large-billed Crows segregate based on feeding sites. There was an overlap between the feeding sites of Carrion Crow and Rook, but only when residual post-harvest rice grains in paddy fields were abundant. Such dietary preferences and differences in foraging habitats may allow the co-existence of these three species within the same locality.
