Endemic to eastern Asia, the Japanese marsh warbler Megalurus pryeri is classified as “vulnerable” in the IUCN Red Data List. Very little information is available concerning the breeding biology of this species. From April to July 2004, we studied the breeding ecology of M.pryeri sinensis in Zhalong Nature Reserve, in northeastern China. The breeding season extended from late May until early August, with a peak in mid-June. Nest building and care of the young was undertaken primarily by females. Males defended their nesting territories, and drove away male intruders. The eggs of the Japanese marsh warbler are white, with tiny fawn spots (greatest diameter=16.88±0.86 mm,n=14); shortest diameter=12.76±0.51 mm,n=14). Clutch size averaged 5.4±1.2 (range 4-7 eggs, n=38 clutches). Incubation lasted for 10-13 days (Mean=11.9±0.8 days, n=18), with a hatching success of 59.9%. The nestling period (range 9-12 days, Mean 10.1±0.9 days, n=15) resulting in a fledgling success rate of 67.5%. Total breeding success was 41.4%. The main cause of nesting failure include human disturbance (cutting reeds), predation, and effects of grazing and flooding.
