Record-breaking numbers of Nordmann's Greenshank-how can that be?

Author: Lin ZHANG

Nordmann's Greenshanks at Yangkou © Jinghua Qian

In 2008, Xiaoyangkou in Rudong, Jiangsu, China was reported as a key site for Spoon-billed Sandpiper (SBS) and Nordmann's Greenshank (NG) and many others. Search in adjacent similar habitats reached Tiaozini, Dongtai in 2009, with small numbers of Nordmann's Greenshank recorded in both northward and southward migrations. Here we describe how the count number from two digits can reach four digits at the World Heritage site-Tiaozini. Earlier counts are not discussed here (e.g. the ones made by Mark Barter and Yancheng National Nature Reserve in the 90s).

Xiaoyangkou has been regularly monitored since 2008 due to efforts from China Coastal Waterbird Census. Extensive seawall constructions makes waterbirds counting easier and easier as when the supratidal mudflats become construction sites inside seawalls, most waterbirds feeding on intertidal mudflats have to get altogether in limited number of artificial high tide roosts close to seawalls. Thus on many days they can be counted in decent view without the need of very high tides. Progress of seawall construction is slower at Tiaozini. When tides are not super high, and when small numbers of SBS and NG haven't been able to raise funds to support decent logistics, observations are made mostly by foot and often by single observers on single days. There's no obvious increase in the amount of NG recorded in this period.

Markers 2009 and 2010 show where observations were made when Tiaozini Car Park was still part of intertidal mudflat. Jianggang is the closest town.

With the findings of 100+ SBS in Rudong, more conservation efforts are made with support from EAAF SBS Task Force. In Sep and Oct, when the number of SBS reaches its peak, 10+ observers with several vehicles become reasonable to cover much larger areas in consecutive days. Seawalls south and north of Tiaozini Car Park are closed soon which makes it possible to drive vehicles to follow the movement of waterbirds when tide rises and forces them into high tide roosts inside seawalls.

Markers Hightide Roost, Wetland Park and HTR North show some main spots to make good counts。

Wetland Park as a high tide roost is next to Tiaozini Car Park and birds moving from intertidal mudflat into it can be easily noticed. Large flocks of NG are noticed here when SBS survey is being conducted. A count of 800~1000 here plus the numbers from Rudong reaches a total of 1000~1200 (population of 600~1000 in EAAF by then). Photos collected also indicate as SBS, NG gather here to do complete moult in southward migration.

The titled article was the very first to describe the large number of Nordmann's Greenshanks in the southern Yellow Sea. It shows there were 1117 Nordmann's Greenshank on the Jiangsu coast in 2015.

Nordmann’s Greenshanks and other waders at Tiaozini © Dongming Li

Even with those findings, NG still cannot get as much attention as SBS, and stays in the IUCN category as EN, probably because it doesn't have a charismatic spoon. Counts of NG are mostly still by-products of SBS surveys.

As the areas inside seawalls are built into aquaculture ponds and farmlands, many of those hightide roosts are not suitable anymore. Wetland Park as a preferable spot for hundreds of NG becomes a wetland park in the same style with that of thousand of wetland parks in China, the style of nice-looking gardens in human eyes but unfriendly in birds' eyes-with deep water and steep banks, unfriendly to NG but maybe friendly to a few Moorhen and Little Grebe. NG has to move elsewhere to look for high tide roost, incl. the remaining Breeding Colonies of Saunders's Gull at the northern end of Tiaozini reclamation area after it became World Heritage in 2019.

In 2020, when the erosion of intertidal mudflat out of seawalls reaches its extreme, number of tourists visiting this WH also reaches much higher level. NG and all the other waterbirds are too shy to stay at the last remaining bit of mudflat at high tide here and have to fly over seawalls to roost.

Mudflat south of Tiaozini Car Park before 2015. It's possible to walk on the mudflat for several km to observe waders.

At the end of 2019, tidal creek has moved much closer to seawall. White lines show where the tidal creek reaches in 2020. Wader observation by foot can be made only in the area circled by white lines.

In monsoon season, water level becomes too high for the nesting Saunders's Gulls and local managers lowered the water level which ensures the safety of nesting birds but also provides the best high tide roost for large to medium waders incl. NG. In late June, the start of southward migration, we have already welcomed tens of NG there.   

Breeding Colonies of Saunders's Gull etc.

After Saunders's Gulls' chicks have fledged, there's no more control on water level there and it becomes too high again for NG to roost. Meanwhile local government rents an aquaculture pond next to Tiaozini Car Park as a high tide roost for waterbirds(HTR720).

Marker HTR720 is the high tide roost where 1100+ NG gather.

Currently HTR720 is probably the only proper high tide roost in the range of 10+ km from Liangduo Rivermouth in the north to Fangtang Rivermouth in the south. It attracts almost all kinds of waterbirds, from small ones e.g. SBS to big ones e.g. Black-faced Spoonbill, and medium ones incl. 1100+ NG.

The big number of NG may be celebrated, meanwhile worrying. As we observe, NG feeding on intertidal mudflats south of Fangtang River have no good high tide roost nearby and fly to gather in HTR720 with the ones coming from south of Liangduo River. Such a large population using a single roost together with tens of thousands of other waterbirds can face challenges e.g.   infectious disease (please don't forget Covid-19 pandemic in human being). Cases of massive death has happened eg. at Wetland Park when it serves as one of the best high tide roosts (although reasons unknown).

Dead birds count (Source: unpublished data from SBSinChina).

Dead waders in autumn 2014 (provided by SBSinChina).

Furthermore, there are several other sites across the Yellow Sea serving as staging grounds for NG to do their annual complete moult. Many of these sites are not properly monitored, often due to lack of flagship species such as SBS. Whether these NG using these sites have to abandon them due to habitat deterioration and move to Tiaozini to stage needs further study. Concentration at a single site in such large scale, either <1000 or >1100, doesn't necessarily mean the flyway population of NG is increasing or the threats they face are decreasing.

Fixes of a sat-tagged NG near Tiaozini in southward migration in 2018（unpublished,courtesy of CY Choi and CX Yu）. High tide roosts the NG uses include the Wetland Park and Breeding Colonies.