Recent Increase of Nesting on Utility Poles by the Black-billed Magpie Pica pica sericea

Abstract

A study on the nest-site preference of the Black-billed Magpie Pica pica sericea was conducted in northeastern Saga City, northern Kyushu, Japan. In first nesting, the proportion of magpie nests on utility poles was significantly greater than expected from random nesting. However, the proportion of nests on utility poles in repeat nesting decreased in comparison to first nesting. Incomplete nests occurred more frequently in trees than on utility poles, suggesting that, if they selected trees, magpies carried nest material to more locations before settling on a suitable nest site. Pairs nesting on utility poles achieved higher nesting success than those nesting in trees. The percentage of complete magpie nests on utility poles increased from 41% in 1991 to 55% in 1994. Nesting on utility poles may be among the possible reasons for the recent geographic expansion of magpies in Japan.