抄録
Nest site availability is an important factor promoting the establishment of introduced bird species. Since the 1990s, the Eurasian Magpie Pica pica has colonized an area of southwestern Hokkaido, in northern Japan. In this study, we investigated the characteristics of magpie nest sites in Tomakomai, Hokkaido, at multiple spatial scales: home range, territory, and microhabitat, in order to understand the environmental factors that have supported the magpie’s successful establishment. We found 67 nests (49 on trees; 18 on artificial structures) in May 2011. We analysed nest locations and surrounding land use, using nest presence/absence data and a logistic regression analysis, in order to reveal preferable environments for magpies. At the home range scale, the urban environment positively influenced nest presence. We also revealed by territory scale analysis that magpies used tree-dense patches when nesting on trees, while magpies built nests on artificial structures when tree density was relatively low. At the microhabitat scale we found that magpies preferred to nest at higher positions in nesting substrates. These results suggest that magpies are flexible in their nest site selection in the urban environment, depending on the complexity of the surrounding land use, tree density and substrate heights, at each spatial scale. This conclusion provides new insight into the successful establishment of magpies in Hokkaido.
