Egg-dumping by the Moorhen, Gallinula chloropus, in Japan

Abstract

The Moorhen Gallinula chloropus is a well known intraspecific brood parasite.However, there has been no reports on brood parasitism of the Moorhen in japan. During a 8-yr field study of marsh nesting birds in Akigase marsh, central japan, we found some Moorhen nests which contained abnormally large number of eggs (super-normal clutch) and we obtained evidence of intraspecific brood parasitism and/or cooperative nesting. Moorhens were unable to distinguish between foreign (Japanese Quail and conspecific) and their own eggs. A proximate cause of frequent egg dumping may due to the high breeding density in the habitat. This is the first report on the egg-dumping in a Japanese population of the Moorhen.