The breeding abundances and habitats of Water Rails Rallus aquaticus and Ruddy Crakes Porzana fusca were surveyed from mid May to late August of 2005, and mid April to late August of 2006 in the Watarase Marsh, central Japan. Presence of the birds was confirmed by response to species-specific calls broadcast from a handheld cassette player. Twenty out of 110 survey sites in 2005, and 16 out of 140 survey sites in 2006 were confirmed to be occupied by Water Rails. The number of sites occupied by Ruddy Crakes were limited to two sites during each of the two survey years. The abundances of these species were estimated to be 12 in 2005 and 10 in 2006 for Water Rails, and one each in 2005 and 2006 for Ruddy Crakes. The habitat type where the rails and crakes were confirmed present during the survey was wet reed with dense undergrowth, such as Carex spp. in standing water less than about 20cm in depth. No response was recorded at dry sites with dense tall vegetation lacking undergrowth. The restricted distributions of these two breeding wetland species in the Watarase Marsh may be related to an apparent decrease in the wettest habitat types. I recommend the restoration of wet habitat at Watarase Marsh. Management techniques such as scouring the reed floor may result in an increase of suitable habitat for wetland birds such as the rails.
2006 by Japan Bird Research Association