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Location Japan, Chiba,Ibaraki
Central coordinates 140o 38.00' East  35o 52.00' North
IBA criteria A1, A3, A4i
Area 2,300 ha
Altitude 0 - 10m
Year of IBA assessment 2004

Wild Bird Society of Japan

Site description The site is one of the few breeding sites of Japanese Marsh Warblers.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Whimbrel Numenius phaeopus passage  2004  present  A4i  Least Concern 
Marsh Grassbird Locustella pryeri breeding  2004  present  A1, A3  Near Threatened 
Ochre-rumped Bunting Emberiza yessoensis breeding  2004  present  A3  Near Threatened 

IBA Monitoring

2010 low not assessed negligible
Poor - based on little, or potentially unreliable/unrepresentative, data

Invasive & other problematic species, genes & diseases invasive non-native/alien species/diseases - unspecified species likely in long term (beyond 4 years) some of area/population (10-49%) no or imperceptible deterioration low

Little/none of site covered (<10%)  Unknown  Unknown  negligible 

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Suigo - Tsukuba Quasi National Park 34,309 unknown 0  


IUCN habitat Habitat detail Extent (% of site)
Wetlands (inland) Riverine floodplains  -
Artificial - terrestrial Abandoned farmland, disturbed ground  -

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Tonegawa floodplain. Downloaded from on 22/10/2016

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