The Eurasian Magpie

Abstract

The Eurasian Magpie Pica pica is thought to have been introduced into northern Kyushu, Japan, from Korea during the 16^th century. Several small populations became established in the Chikushi Plain, but failed to expand their geographic ranges. However, from the mid 20th century onwards, and most remarkably since the 1980s, the size of the population and the extent of the range have increased. In this paper, I review the studies conducted on the ecology, social system and life history of magpies and discuss factors determining the distribution and population dynamics of magpies in Japan.
On the one hand magpies are omnivorous, and flexible in their nest-site preferences. They utilize artificial structures, as well as natural sites (particularly trees in rural areas), for nesting, and lay large clutches, which facilitates their establishment in new habitats. On the other hand, magpies do not make long distance movements due to their morphological characteristics and strong natal philopatry, and prefer open habitats. Forested hills have presented ecological barriers preventing magpies from expanding their distribution - until recently. Habitat change, including the development of residential areas in hills, may have contributed to their recent range expansion.
The magpie’s recent population increase in northern Kyushu is attributable to a combination of steady urbanization and adaptation by magpies to the urban environment. From the 1980s onwards there was a rapid increase in the use of utility poles for nesting by magpies leading to an increase in numbers. However, continued urbanization negatively impacted nesting success and since the 1990s the number of nesting magpies has been in decline, probably resulting from deterioration of the urban foraging environment.
The magpie has invaded urban environments in Japan and elsewhere in Eurasia. It is useful to conduct long-term monitoring of the dynamics of such populations, and to investigate the breeding ecology, life history and social structure of this species in order to elucidate the factors determining the success or failure of an avian invasion.