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The site was identified as important in 2004 because it was regularly supporting significant populations of the species listed below, meeting ('triggering') IBA criteria.

Populations meeting IBA criteria ('trigger species') at the site:

Species	Red List1	Season	Year(s)	Size	IBA criteria
Whimbrel Numenius phaeopus	LC	passage	2003	present	A4i
Terek Sandpiper Xenus cinereus	LC	passage	2003	present	A4i
Grey-tailed Tattler Tringa brevipes	LC	passage	2003	present	A4i
Saunders's Gull Saundersilarus saundersi	VU	winter	2003	present	A1

1. The current IUCN Red List category. The category at the time of the IBA criteria assessment (2004) may differ.

Ideally the conservation status of the IBA will have been checked regularly since the site was first identified in 2004. The most recent assessment (2015) is shown below.

State (condition of the trigger species' habitats)
Habitat	Quantity (% remaining)	Quality (% carrying capacity)	Result
Marine Intertidal	good (> 90%)	moderate (70-90%)	near favourable

Pressure (threats to the trigger species and/or their habitats)
Threat	Timing	Scope	Severity	Result
Residential and commercial development	happening now	some of area/population (10-49%)	moderate to rapid deterioration	high
Biological resource use	likely in long term (beyond 4 years)	some of area/population (10-49%)	slow but significant deterioration	medium
Invasive and other problematic species and genes	likely in long term (beyond 4 years)	some of area/population (10-49%)	slow but significant deterioration	medium
Energy production and mining	happening now	small area/few individuals (<10%)	very rapid to severe deterioration	low
Human intrusions and disturbance	past (and unlikely to return) and no longer limiting	some of area/population (10-49%)	no or imperceptible deterioration	low

Response (conservation actions taken for the trigger species and/or their habitats)
Protected areas	Management plan	Other action	Result
Little/none of site covered (<10%)	No management planning has taken place	Some limited conservation initiatives are in place	negligible

Year	Protected Area	Designation	% overlap with IBA
1954	Oita Prefectural Fisheries Coordination Regulations Article35(1)(i)	保護水面	1
1966	Oita Prefectural Fisheries Coordination Regulations Article35(1)(ii)	保護水面	1
1966	Oita Prefectural Fisheries Coordination Regulations Article35(1)(iii)	保護水面	1
1973	Fudokinooka	都道府県指定鳥獣保護区	1
1979	Buzenkai	沿岸水産資源開発区域	89
1980	Yamakunigawa	都道府県指定鳥獣保護区	5
1981	Hachiya	都道府県指定鳥獣保護区	10
2003	Common fishery right area(Fukuoka)	共同漁業権区域	10
2004	Common fishery right area(Oita)	共同漁業権区域	88

Habitat1	Habitat detail	% of IBA
Marine Intertidal		major (>10)
Marine Neritic		major (>10)

1. IUCN Habitat classification.

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Nakatsu and Usa tidal flats (Japan). Downloaded from https://datazone.birdlife.org/site/factsheet/nakatsu-and-usa-tidal-flats-iba-japan on 23/11/2024.