China Report

RED KNOT NORTHWARD MIGRATION THROUGH BOHAI BAY, CHINA

FIELD TRIP REPORT APRIL & MAY 2011

 Chris Hassell   Adrian Boyle   Matt Slaymaker

 Introduction 

The ecology of the enigmatic long-distance migratory shorebird Red Knot Calidris canutus, despite a lot of study, is still not fully understood in the East Asian-Australasian Flyway (EAAF).

It is represented in this flyway by two subspecies piersmai and rogersi; they breed in different locations in the Siberian Arctic and share non-breeding locations in Australasia (Rogers et al. 2010).

One of the mysteries of the  species was where they stop-over during their northward migration. Surveys of the Yellow Sea by Mark Barter and Chinese colleagues failed to find significant numbers of the species despite extensive searching.

They did record 14,277 in the NW Bohai Bay region during spring migration 2002 (Barter et al. 2003). During a brief 6-day visit in late April 2007 Chris Hassell (CH) from Global Flyway Network (GFN) counted a single flock of 10,650 Red Knot in the same region.

In September 2007 Yang Hong-Yan (YHY, Beijing Normal University) commenced a PhD project on the food, foraging and stopover ecology of Red Knots in the area. She has been conducting regular counts since 2003 during the spring period of northward migration and her work shows that numbers of birds in the study area have increased over the years, presumably due to habitat destruction elsewhere and consequently birds moving in to the study site (Yang et al. 2011).

It is clear from our current knowledge this site is the single most important site for Red Knot on northward migration in the EAAF. The southward migration route of Red Knot is still a relative mystery to us. Along with the work by YHY, studies by GFN have continued during the northward migration seasons of 2009, 2010 and 2011. These field studies have concentrated on searching for individually marked birds and have been remarkably successful. 

In view of the many human-related threats to what would seem to be the single most important staging area for two subspecies of Red Knot, encompassing all Red Knots wintering in Australia and New Zealand, it seemed of utmost importance to continue the survey work.

This need was recognized by WWF-Netherlands and WWF-China who continued to fund the field work in 2011 through their association with GFN (CH remained supported by BirdLife Netherlands). Beijing Normal University also funded aspects of the project. Here we report on what we have achieved in April- May 2011. All the migratory birds mentioned in this report are covered by the China-Australia Migratory Bird Agreement (CAMBA) and it should be a source of embarrassment to both governments that this destruction of critical habitat to migratory birds is happening unregulated and unabated.

 The Study Site:

 The centre of the study site is situated at 39o 03’ 35”N 118o 12’ 33”E. It is near Nan Pu Development City, situated on the edge of Bohai Bay, 190 km south east of Beijing, China see figure 1 below

Figure 1. Interpreted satellite image of Bohai Bay, China. 

 The image shows the 3 study sites and the Caofeidian New Area Industrial Park. This enormous area will have destroyed 142 sq/km of inter-tidal mudflat at its completion in 2020 (Yang et al. 2011). It has already covered >75% of its planned area.

The mudflats of the 3 study sites used to give a 25km long and 1-3km wide (on the lowest tides) foraging area for shorebirds. This is no longer the case as most of the Zuidong mudflats have been claimed for industry and the remaining flats at the Zuidong site seem to get little use by shorebirds (see details further in the report).

The mudflats are separated from the Bei Pu Salt Ponds by a man-made seawall. These salt works are reputedly the largest in Asia’. This area that is adjacent to the mudflats, is also good habitat for birds to forage and roost but it is also being lost to industry.

Marking of Shorebirds 

Shorebirds captured throughout the East Asian Australasian Flyway (EAAF) are marked with plain coloured flags, engraved leg flags (ELF), or combinations of 4 colour-bands and 1 flag.

Each bird also has an individually numbered metal band placed on it supplied by The Australian Bird and Bat Banding scheme (ABBBS). Each capture location has its own coloured flag and/or position of the flag on the birds’ leg.

The focus of our study is the individually colourbanded birds from Roebuck Bay, Broome NW Australia, but we record every single flag we see during our field work thereby documenting the importance of this area to various species from throughout the flyway. 

 Human Use of the Mudflats

 The birds share the mudflats and food resources with the human population. The shell-fishers are able to harvest huge amounts of bivalves from the highly productive mudflats that comprise our study site.

This economic benefit to local people is very real, the income is in the region of 10 million RMB (A$1.4 million) (Yang, pers.comm.) and as the mudflats are gradually destroyed their livelihood is threatened. 

We recorded a team of 18 men with 7 pumps bringing in a minimum of 100 sacks of shells (a minimum of 5 tonnes) returning from work on a single tide-cycle on 17 May. This productivity seemed to last throughout our 7 week study period and the tidal-flats are worked for about 6 months each year (Yang, pers.comm.).

 Field work in 2011

 In 2011 the fieldwork program started just 7 days later (9 April) and finished 2 days later (30 May) than the 2010 work. There were not significant numbers of Red Knot in the study area during the first week of April.

When Adrian Boyle (AB) and Matt Slaymaker (MS) arrived at the site some species of shorebird had already arrived in good numbers from their southerly non-breeding areas, but there were only 52 Red Knot present.

Numbers rapidly increased to >1700 by 14 April and the peak of 66,500 were present during the count on 13 May. This peak of 66,500 Red Knot is the biggest count in the study site. It is only a small increase on the 2010 peak number but is considerably higher than 2009 and a full 63% increase on the peak of 2008.

This would suggest that the destruction of surrounding mudflats is compressing the Red Knot populations using Bohai Bay in to an ever decreasing area that is our study site.

Table 1 below shows the increase in peak counts.

Table 1. The increase in peak counts of Red Knot at our study sites between May 2008 and May 2011 (Yang et al. 2011 in an unpublished data.)

There were some differences from the previous years. In 2009 and 2010 many birds chose to roost in salt ponds in close proximity to the mudflats and consequently the majority of our observations were done on the roosts. The roosts are relatively undisturbed (compared to our other study site at Roebuck Bay), and although migrating raptors and salt pond workmen do cause some disturbance, it is not significant.

 However, this year, particularly later in to May, the majority of Red Knot flew many kilometres inland at or close to high tide. We were able to follow their flights with binoculars and telescopes but not on foot or with our vehicle.

The area of salt ponds and therefore roosting opportunities is vast, stretching 10km inland and across the entire 20km, from east to west, of our study sites (see Fig 1, study site image).

It is not feasible to access the majority of this area. We did find some roosts and foraging Red Knot as we drove to and from the core area of our study site but the roosting birds were always distant and often in shallow water so we rarely got the opportunity to scan them at these sites. The myriad roosting opportunities is a positive for the birds but, of course, if there are no productive foraging opportunities then all the safe roosting sites in the world won’t be any use.

Due to the birds roosting at inaccessible locations we concentrated our resighting efforts out on the mudflats more so than in previous years. This proved successful when big numbers of birds were present but the tides also need to be suitable.

The scanning of resting flocks at roost sites and foraging birds on the inter-tidal mudflats occupied the majority of our time and a remarkable haul of sightings were recorded (see Table 2).

Table 2 below shows the totals of all migratory shorebirds (plus 2 gulls and 1 tern) recorded during the field work and the location they were originally marked at. The birds with plain flags just indicating the original banding location cannot be identified to the individual level.

The colour banded birds and the engraved leg flags (ELF) can be attributed to individual birds and these birds with numerous sightings show very interesting ‘life histories’ (see appendix 1). As the team were seeing individually marked birds that were ‘new’ to the area late into the field work period, it is not unreasonable to assume that plain-flagged birds were also still arriving or had escaped our attention previously, while others will have moved on. So while some will undoubtedly be multiple sightings, the numbers seen appear to be a good reflection of the numbers of flagged birds present.

These records represent 18 different marking areas in the EAAF. In relation to the total number of sightings this is a 9.6% increase compared to 2010 (3146). Records of individually colour-banded birds from NWA increased by 27%; in relation to the 2010 total. GFN and AWSG had a good marking season of colour-banded Red Knot in North West Australia from August 2010 to April 2011 and that cohort of birds undoubtedly increased our sightings.

Figure 2. The map above shows the different banding areas that we recorded Red Knot from during both 2010 and 2011. Due to the size of the map not every area can be seen. We recorded Red Knot at Bohai from Chukotka, Kamchatka, Sumatra, Chongming Dongtan (China), 3 areas in Australia and both north and south islands of New Zealand.

Use of the Mudflats and Resighting Coverage

 The use of the 3 study sites (see Fig. 1, Study Site image) has changed from our first visit in 2007. The Zuidong area is now >50% destroyed by mud pumping and the construction of sea walls. These walls still contain sea water but the ‘tide’ does not come and go to reveal the mud the birds need to forage on.

Although the remaining tidal flats at Zuidong are still open to the sea and have a ‘normal’ tidal regime, the mudflats are used by a fraction of the birds from previous years.

The method of pumping the mud over the sea wall into the adjacent salt ponds and then letting the water drain back out, leads to huge volumes of water and anaerobic mud washing back over the ‘healthy’ mudflats and rendering them very poor quality habitat for shorebirds.

Presumably the anaerobic mud settles on the top of the healthy mud and suffocates much of the benthos. The favoured food of Red Knot, a bivalve, Potamocorbula laevis, feeds on algae on the mud surface and this algal layer is destroyed by anaerobic mud.

In addition to this issue, at least one of the pumping boats were working only 800m from the seawall which is right in the preferred zone for Red Knots to forage (at about one kilometre from the seawall.

Our records of marked birds and the general populations this season showed that when birds arrived in the study site they did forage at Zuidong, but quickly abandoned it; presumably due to a lack of available and suitable food.

A very simple but very stark example of the poor quality of the Zuidong mudflat in 2011 is shown below (YHY unpublished data) in table 3.

Table 3.

Peak numbers of all shorebirds and Red Knot using the Zuidong mudflats during 2009 - 11.

 The destruction of the mudflats at Beipu, the most westerly of our study sites, started in March 2011.

For the whole 7 weeks we were in the field, the Beipu seawall was very busy with trucks, large machinery cars and construction workers.

It was often impassable to our vehicle and while we did manage a few resighting scans at this site, eventually on 23 May, we were requested by a manager of one of the development companies not to access the mudflats.

We managed one more count from the seawall, but with small numbers of Red Knot present it became counter-productive to go there.

The Nanpu mudflats are still relatively undisturbed. They have had some pumping done a few years ago (2006) and artificial islands have been built close off-shore for oil drilling and oil tanker loading but the mudflats abutting the seawall are still good areas for shorebird foraging.

However, we did see birds with oil contamination on their feathers during our telescope scans and small amounts of oil washed up on the sea wall.

In 2007 and 2009 we recorded the majority of our marked birds from this area, Zuidong.
In 2011 we recorded almost none.© A Boyle

 The source of this is likely to be the nearby oil derricks and tankers, but in July 2010 there was a huge oil spill from an explosion in an oil pipeline in Dalian 280km east of our study sites. 

In June and July 2011 there was another large oil spill at sea on the ConocoPhillips/China National Petroleum Corporation, Penglai Rig 170km east of our study sites.

These industrial accidents affect the whole biodiversity of the area and highlight the immense pressure on the entire Yellow Sea eco-region from human impact.

The Nanpu mudflat is where most of the birds congregate and subsequently where the vast majority of our field work was done this year. Viewing can be done from the seawall during the smaller tides and out on the flats during the spring tides.

However, even after 7 weeks the birds were still a little unpredictable and would sometimes leave the mudflats a full 4 hours before high tide even when there appeared to be large areas of suitable mud available for them to feed on.

Despite this we had great success and during the last three days of field work we recorded 26, 40 and 50 individually colour-banded Red Knot from NWA. This is in addition to everything else we saw and remember 6400km away from the marking site of these birds!

All these resightings were on the mudflat. We did not know where the birds were roosting during these final days but it appeared to be well inland.

One issue with the field work in 2011 was that we left the study site too soon. In our previous experience the vast majority of Red Knot have left Bohai by 30 May. This was not the case this year with a minimum of 7420 still present on 31 May (Yang unpubl. data), a day after our last day in the field.

Pipes heading to Beipu © A Boyle

China Update 

 It has been busy since the last update. People arriving, people leaving, a conference and we saw some birds too.

The team doubled in size with the arrival of Theunis Piersma, Sytze Pruiksma from the Netherlands and Bob Gill from Alaska. They joined us in the field for a few days before attending the Seminar on ‘Shorebirds and Coastal Wetlands Conservation in the Yellow Sea Eco-region’ on the 18th and 19th.

Organised by WWF China, the aim was to gather together concerned parties from China and further a-field to discuss the problems facing this site and try to find realistic solutions. Other participants included an advisor to the Chinese Government from the Academy of Sciences, various staff from WWF China, various State Government officials, various biologists from Chinese Universities including Miss Yan Hong Yan (who we work so closely with), Phil Battley from New Zealand and numerous media outlets.

 Day one was spent hearing talks from many and varied participants about the area and shorebird research while the second morning was spent in the field giving the participants the opportunity to see the site.

After a brief stop in the saltpans to see impressive flocks of Curlew and Sharp-tailed Sandpipers we went to Nanpu to view birds feeding on the mudflats. As well as the 1000’s of Red Knot we saw a single Nordmann’s Greenshank and, to the delight of the guys from WWF Hong Kong, a Curlew Sandpiper with white over yellows flags.

From here we went to Zuidong to see the continuing devastation and the mud-pumping boats building the sea-wall and the ‘desert’ of dry mud that was once salt pans with feeding and roosting shorebirds.

The two days seemed to go well and we hope that some of the ideas raised can be acted upon before it’s too late … time will tell.

Unfortunately Ady was unable to attend as he left us on the 16th. We are very envious of his trip to Alaska and are putting extra hours in the field trying to find something really good to get back at him. It just doesn’t feel normal here without him.

The Albo-plover is still present but has only been seen a couple of times recently as we aren’t spending as much time scanning on the roosts. Nordmann’s Greenshank numbers increased again, this time to at least 9 individuals. Marsh Sandpipers have moved on dropping from 10s of thousands of birds in the Saltpans to just a few scattered individuals. They have, however, been replaced by Curlew Sandpipers which, unlike last year, seem to be prefer the Saltpans to the mudflats. Every morning as we drive to the mudflats we see impressive flocks wheeling over the pans.

 Red Knot scanning has been very good with large numbers of birds to look at. Our new tactic of walking out on to the mudflats and observing feeding birds has been particularly productive. In the last few days however, many appear to have departed. Numbers have halved and sub-species scans have shown a very noticeable swing in favour of piersmai birds. This is line with our data of the last two years as rogersi, that are predominately from New Zealand and South east Australian non-breeding areas, head off to their far east Siberian breeding grounds of Chukotka before piersmai (predominately from north West Australia) head to their New Siberian Island breeding grounds. We are also seeing more birds that were marked in Broome so there seems to have been a late influx as well.

Birding away from the mudflats has been limited. A couple of visits to ‘Tree Lane’ (a new one we’ve found where the trees are still standing) have produced Black-naped Oriole and Grey-sided Thrush as well as a selection of migrant warblers and flycatchers. Black Drongo have arrived and a second wave of Amur Flacons caused panic among the shorebirds with over 30 recorded coming in off the sea on the 13th. 

One thing that will decrease in quality now Ady has left is the standard of photographs accompanying these updates…just normal ones from now on.

Matt and Chris

Habitat Destruction

The field work at the study sites is challenging, not so much from a practical point of view as there are good roads towards the sites and accessible tracks along the sea wall, but it is mentally challenging to work in an area that is having prime shorebird habitat destroyed as we watch the birds. The sense of a rapidly growing economy (progress or destruction?) is palpable. The noise of large machines, pumping boats and the smell of diesel all make for a rather depressing environment. The birds still persist, despite all the development pressures, can be seen feeding in large flocks surrounded by this.

 The pumping boats are pumping mud from the intertidal flats, to a depth of 15m, through pipes and over the seawall into the adjacent salt ponds. This is to create ‘solid ground’ that can then be developed with industry. At the same time new sea walls are being built around the mudflats and this area is then filled in and developed. This method of ‘reclamation’ is widely used in the Yellow Sea and is very effective for its purpose.

Enormous areas of inter-tidal mud flats have been converted to industrial land in this way. The China Marine Environment Monitoring Centre estimates that between 2006 and 2010 1000 km2 of land were reclaimed each year in China. In addition to this pressure the Bohai Sea is the most polluted sea in the world and absorbs nearly 5.7 billion tonnes of sewage and 2 million tonnes of solid waste each year. 43 of the 52 rivers that flow into it are heavily polluted (the China Marine Environment Monitoring Centre website).

Large flocks of Red Knot still use the heavily disturbed habitat © A Boyle

Salt Ponds 

Our field work is focused on Red Knots using the intertidal habitat, but the salt ponds that are adjacent to the mudflats are important habitats in their own right. Red Knots use them to roost in and occasionally to forage in when strong winds move the shallow water over the larger ponds thus exposing wet, soft sediments that can be exploited by numerous ‘tidal-flat species’.

 Some species notably Curlew Sandpiper (Calidris ferruginea), Marsh Sandpiper (Tringa stagnatilis) and Black-tailed Godwit (Limosa limosa) do most of their foraging in the salt pond habitat and rarely visit the intertidal zones.

These species feed in shallow water up to their flanks or pick along the fringes of the ponds. The wind conditions make a difference to where they feed. As mentioned previously, accurate observations in these vast ponds are difficult but we see tens of thousands of Curlew and Marsh Sandpipers in the ponds and many 1000’s of Black-tailed Godwit. The Black-tailed Godwits are fascinating; to our eyes they look huge in comparison to the melanuroides subspecies that we are familiar with in North West Australia and nearly all of them we observe are in non-breeding plumage.

A Curlew Sandpiper Calidris ferruginea marked in NWA in a salt pond © A Boyle

Nordmann’s Greenshank Tringa guttifer

Nordmann’s Greenshank is an endangered shorebird (IUCN 2001) with a continuing decline in its population. During our field work we saw up to a maximum of 9 on any one day. Nordmann’s Greenshanks were recorded on 25 days between 22 April and 19 May. We saw them feeding on the mudflats and feeding and roosting in the adjacent salt pans.

Nordmann’s Greenshank Tringa guttifer roosting in a salt pond © A Boyle

Seminar

On 18 and 19 May WWF-China had organized a Seminar on ‘Shorebirds and Coastal Wetlands Conservation in the Yellow Sea Eco-region’. The aim was to gather together concerned parties from China and further afield to discuss the conservation implications of the industrial development of the area and try to find realistic solutions.

Other participants included an advisor to the Chinese Government from the Academy of Sciences, various staff from WWF-China, various State Government officials, various biologists from Chinese Universities including Miss Yan Hong Yang (whom we work so closely with), Theunis Piersma (GFN), Bob Gill (USGS) and Phil Battley (Massey University, New Zealand) as well as several media types.

Day one was spent listening to talks from the many and varied participants about the area and shorebird research, while the second morning was spent in the field giving the participants the opportunity to see the site.

After a brief stop in the saltpans to see impressive flocks of Curlew and Sharp-tailed Sandpipers we went to Nanpu to view birds feeding on the mudflats. As well as the 1000’s of Red Knots, we saw a single Nordmann’s Greenshank and, to the delight of the delegates from WWF-Hong Kong, a Curlew Sandpiper with white over yellows flags which had been marked in WWF’s Mai Po Marshes Reserve.

From here we went to Zuidong to see the continuing devastation and the mud-pumping boats, the sea-wall building and the ‘desert’ of dry mud that was once salt pans with feeding and roosting shorebirds.

The two days seemed to go well and we hope that some of the ideas raised can be acted upon before it’s too late … time will tell.

We also had a famous Friesian musician with us, Sytze Pruiksma. He performed his original compositions and was extremely popular with the audience. I would like to reiterate how important this meeting was and thank WWF-China for their hard work in bringing us together.

The Future of Research

GFN, with continued funding from BirdLife-Netherlands, will continue to document the fates of several shorebirds at their ‘wintering’ destination in Roebuck Bay, northwestern Australia, applying individual colourband combinations and ELF’s and conducting intensive re-sighting scans for the marked birds and building up a comprehensive database of sightings from the marking site and throughout the flyway.

With the work in Bohai Bay and sightings from other shorebird colleagues throughout the flyway, particularly in New Zealand and China (Chongming Dongtan and Yalu Jiang National Nature Reserves), we will be able to assess the effects of human induced habitat change through survival analysis statistical work.

Passerine Migration

Although the migratory shorebirds were the focus of our work, because we had a number of keen ornithologists present, whenever we weren’t studying shorebirds we were looking for anything with wings! The passerine migration through the area is marked by species diversity despite the paucity of any wooded habitat. Appendix 2 below has a complete list of all the birds seen during the field work period and includes some rare and difficult to see species. Three of the more common and colourful species are shown here. 

Acknowledgments

Financial support for this work comes from BirdLife-Netherlands, WWF-Netherlands/WWF-China and Beijing Normal University.

A huge thank you to Yang Hong-Yan, Chen Bing and Mr. Zhao for their friendship and constant help during our field work.

Additional contributions to the field work came from Theunis Piersma, Sytze Pruiksma, Bob Gill and Lei Ming.

We thank Heather Gibbs for answering many and varied questions in relation to the database and updating the database to my every whim.

Thank you to all the shorebird enthusiasts throughout the EAAF who send in sightings of marked birds, and to the NWA 2011 expedition team, in particular Joop van Eerbeek and Mo Verhoeven.

Thank you also to the fabulous group of volunteers from the Broome community who assist with the capture of the birds.
With many Thanks to Liz Rosenberg and Clare Morton for editing this report.

Thank you to Ian Southey for use of his image. Thanks to Kim Onton for figure 5 and Andreas Kim for formatting and presentation.

More information on the GFN colour banding project can be found at :http://www.globalflywaynetwork.com.au

Contact Chris on: turnstone@wn.com.au