Ecology of the Red-crowned Crane and Conservation Activities in Japan

Abstract

There are several ecological differences between the migratory continental population and the nonmigratory Hokkaido population of Grus japonensis. Even though the most cranes of the latter move shortly between their breeding and wintering grounds, a few of the pairs occasionally maintain their same territories year-round. The classic nesting habitat for G. japonensis is an open wetland consisting of reed dominant vegetation. Recently, however, they have shown a tendency for nesting in the thick alder forests, accounting for over 10{\%} of all nesting pairs in 2009. This shift in habitat selection is one of the factors supporting their recent population growth. During the coldest season, cranes concentrate at a few major artificial feeding stations and then roost in neighboring unfrozen rivers. In recent years, however, individuals feeding at minor stations are increasing because the major feeding stations and roosts are probably reaching their capacity limits. The Hokkaido population is continuously growing since the mid-twentieth century, and numbers of cranes exceeded 1500 as of January 2014. Expansion of G. japonensis distribution due to increase in population continues to progress in line with the breeding potential map of Hokkaido. Unfortunately, the population growth is challenged by issues such as (1) the lack of genetic diversity, (2) overconcentration of individuals at a few feeding stations, (3) overcrowding and exceeded carrying capacity in breeding grounds, (4) conflicts with farmers, (5) traffic accidents due to excessive habituation to people, and (6) breeding habitat degradation and disturbance of nesting activities by deer. Therefore, it is urgently necessary to consider future protection measures to maintain the population.