Exciting news! This week (15 October) we published a paper on our decades-long Bar-tailed Godwit research in the East Atlantic Flyway – these are the godwits migrating from West Africa to the Siberian Arctic.
During the last decades Bar-tailed Godwits experienced changes in the tundra phenology. We detected a chain of effects suggesting that conditions in the temperate zone (that is, the Wadden Sea) determine the ability of Bar-tailed Godwits to cope with the climate-related changes in the Arctic.
The paper in Nature Communications can be accessed here. This paper is the product of the collaboration between Russian, USA and Dutch scientists, the migration watchers of trektellen.nl, and two Dutch groups of volunteer bird catchers – VRS Castricum and the Frisian Wilsterflappers. The paper is based on multiple long-term research programs, of which the benthic survey work by the Royal NIOZ in the Wadden Sea needs special mention.
In this blog called, The natural history of our changing planet, Theunis describes the background of this long-term study, and he looks forward: “I hope that our paper helps establish political will to continue such observations. We should realize that, despite its key value, we cannot just rely on the thousands of hours of unpaid labour by keen amateur bird scientists.”
I recently wrote about the excessive amount of snow in northeast Greenland and how shorebirds are struggling to reproduce, and some risk-takers to survive, this year. My blog received a lot of attention: it was also posted on the popular birding webpage Birdguides, Scientific American wrote an article about it and I was invited to the studio of ‘Vroege Vogels’ for a live interview on Dutch national radio.
Now that it is mid-July, which is when usually the majority of Sanderling and other shorebirds in northeast Greenland hatch, I thought that it would be appropriate to write an update of the situation, as well as answer some questions I was asked.
Was this a record late snow melt? How unusual is the situation?
The time of onset and the progress of the snow melt was not abnormal. It was the amount of snow that had fallen in late spring (April and May), when temperatures along the northeast coast of Greenland are still below 0 °C, which was unusually large. Such a large amount of snow just takes a very long time to melt, even though the temperatures in June were normal (on average ca. 5 °C) and it was sunny. Since the establishment in 1996 of the research station Zackenberg, in northeast Greenland (74°28’N 20°34’W), such amounts of snow have never been documented before.
What is the current situation?
My colleagues from Aarhus university, who are still in Zackenberg, reported that the amount of snow in early July was still excessive (80% of surface snow covered on 10 July). Also, a third dead, apparently starved, Sanderling was found. A few more Sanderlings that were ringed in Zackenberg in previous years showed up, but the number of observed individuals observed is still much lower compared with previous years.
Also, these birds do not seem to prepare for breeding, but forage in small flocks apparently to get into condition to prepare for migrating southwards. On 8 July, Jannik Hansen reported: “There are hardly any Red Knots left in the area. Also many Sanderlings have left, and flocks of 10-20 Dunlins are flying around now.” Jannik estimated that only ca. 15% of the area usually used by Sanderlings to incubate is free of snow (in average years, many clutches would hatch around this date), and possibly 2-3 % of the area used by Dunlins.
Northeast Greenland is very large and remote, so there is not a lot of local information. Luckily, we also collaborate with Johannes Lang and Benoît Sittler and their team who work at Karup Elv, on Traill island (72°29’N 23°59’W) ca. 240 km south of Zackenberg. As in Zackenberg, the tundra surface was ca. 95 per cent covered in snow, in late June on Traill island, but on 12 July it was estimated to be only 50 per cent. So snow in the southern part of the NE Greenland national park seems have melted faster than farther northwards.
Johannes initially also reported that the tundra was very silent with very few birds around, but on 12 July they had already found three Sanderling clutches, which are predicted to hatch around 26 July. Johannes reports that he suspects that the clutches were laid in an area that was still snow covered at the end of June. Three Sanderling nests are very few compared to other years when more than 10 nests would have been found by this date at Traill island. Johannes and Benoît still observe Sanderling pairs which they expect to give up reproduction soon. The researchers did not find more than these three Sanderling clutches this year. Their discoveries however indicate that some Sanderling pairs managed to produce a very late clutch despite the excessive snow and its slow melt.
Were conditions similar this year across the entire Arctic?
The Arctic tundra used by breeding shorebirds is very large and snowfall is often a regional weather phenomenon. The entire east coast of Greenland has experienced a lot of snowfall during late spring which took a long time to melt away. We do not know in detail what the conditions were in other parts of the Sanderling breeding range (Pearry land in north Greenland, Ellesmere island in Canada), which use the East Atlantic flyway.
The conditions on the tundra near Barrow, Alaska, where Global Flyway Network collaborator Bart Kempenaers and his team studies Red Phalaropes, Semipalmated sandpipers and Pectoral Sandpipers was also exceptionally late due to a large amount of snow. Much fewer shorebirds were around, but those that waited for the snow to melt eventually bred ca. 1 month later than average.
In the Russian Far East, from Sakhalin to Chukotka, the spring was also cold and late (Evgeny Syroechkovskiy, personal communication), and so was the spring in parts of the Canadian Arctic (Paul Smith in an interview with Scientific American).
In contrast to the situation in Greenland and Alaska, on the Taimyr peninsula in Siberian Russia Global Flyway Network researchers Jan van Gils, Thomas Lameris and Mikhail Zhemchuzhnikov experience a very warm summer with on some days temperatures as high as 22 °C! So snow has melted fast there and the first Red Knot chicks hatched on 8 July. More details in their blog.
Will there be no reproductive success at all for shorebirds breeding in east Greenland?
Next to the already mentioned four Sanderling nests that were found (one in Zackenberg and three on Traill island), a clutch of a Common Ringed Plover was found in Zackenberg on the same snow free patch of tundra of 7 by 15 meter on which the single Sanderling nest was discovered. The Ringed Plover nest was however already discovered and eaten by an Arctic fox –as indicated by the foot prints in the snow next to the nest location- the day after discovery. Also one of the three Sanderling clutches on Traill island fell victim to an egg predator already. I expect that few shorebirds will manage to successfully hatch and fledge chicks this year in Northeast Greenland.
Is a delayed breeding season a problem?
First of all, it should be noted that it seems that the majority of shorebirds did not even attempt to breed, but instead did not arrive in their usual breeding territories but probably stayed further southwards. The few birds that risked to fly to Zackenberg had difficulties to survive the period with lack of invertebrate food, as indicated by the three casualties and the (very) low body masses of birds we caught at the end of June. The few shorebirds that managed to lay a clutch, did so with a serious delay. Because the emergence of insects depends on the timing of snow melt, both birds and their prey are similarly delayed: so what is the problem with a delayed start of breeding for shorebirds?
I suspect low reproductive success of Greenland breeding shorebirds this year, and possibly also a lower survival. I would like to document this, but I can only do so with the help of many observers. You can count the number of adult and juvenile Sanderlings at your beaches until mid November. Please download the manual here, which is also available in French, German and Spanish.
That the extensive snow cover has impacts on the Greenlandic shorebirds can already be observed. Several observers have reported unusually large numbers of Red Knots and Sanderlings in early July, which suggests that indeed many shorebirds that would usually breed in east Greenland have returned early. Jim Wilson reported on 4 July: “Knots in summer plumage have been turning up in UK in the last week and that is too early – even for returning females.” And Klaus Günther, working in the German Wadden Sea reported that “among some 5.000-6.000 Knots the % of adult birds was 25% two days ago [on 2 July] on Sylt! Normally you will see only 1-3 % adults in summer among the grey juveniles.”
It is difficult to say whether (and how) a population will deal with a year with very low reproductive success. The future will tell. I hope that I may count on your continued support with useful observations of colour-ringed Sanderlings and from counts of adults and juveniles in late summer and early autumn.
Is this phenomenon the result of climate change and may we expect this to happen more often?
Information used in this blog was received from Martin Bulla, Jan van Gils, Klaus Günther, Jannik Hansen, Bart Kempenaers, Thomas Lameris, Johannes Lang, Benoît Sittler, Evgeny Syroechkovskiy and Jim Wilson
A report from the 2018 Dutch-Russian expedition in Taimyr. The team members are Mikhail Soloviev, Anastasia Popovkina, Jan van Gils, Job ten Horn, Victor Golovnyuk, Thomas Lameris, Mikhail (Misha) Zhemchuzhnikov and Maria Sukhova:
“It is always a risky business to set up experiments in the field. And especially when the field site is located in northern Taimyr (76.1 N 98.5 E), in Russia, and when the experimental animals are nesting Red Knots.
On 29 May 2018, when Jan van Gils, Mikhail Soloviev and their team arrived in Khatanga, the last human-populated place on their way, there were still many uncertainties about their field season.
Would they be able to arrange a helicopter flight to get back from the field or will they have to hitch-hike an icebreaker and have a compulsory late-summer cruise through Franz-Joseph Land Archipelago? What will be conditions at the Taimyr field site? And, most important, will there be nesting Red Knots?
Everything has worked out so far! The helicopter flight back is agreed upon. The weather has been good most of the time, sometimes even too good, since 22 °C is not what one should expect at this location.
And the Red Knots apparently do their best to make researchers happy. On 9 June they were singing around the field camp, and within a week the team had identified 14 nesting territories.
On 13 June, Job ten Horn found the first Red Knot nest with two eggs. The next one was found by Jan, on 18 June (even though he was nest-searching in a fog). By 24 June, eight nests had been found and 11 Red Knot males had received radio transmitters. On 1 July, the team was celebrating the deployment of the first satellite transmitter. By now, three female Red Knots are being tracked through the Argos satellite service.
Crane flies started to emerge in the first days of July, and there are plenty around. Right in time, as after several days of dog-weather with snowfall last Sunday the first Red Knot chicks hatched! The weather then has become good enough for some researchers to go for a dip in a lake. But it all changed very quick, and on Friday chicks from three clutches met this world for the first time in snow and frost.
Fingers crossed the things will roll on as luckily onwards. Hopefully the many Arctic Skuas nesting in the area and Arctic Foxes wandering around will find something else to eat.”
Jeroen Reneerkens of the University of Groningen studies breeding Sanderlings, for the first time in 2003 and since 2007 annually. He works from the Danish Zackenberg Research Station (74°28’N 20°34’W) in NE Greenland that was established in 1996, and is the research base for various experts monitoring the biotic and abiotic environment of NE Greenland.
Jeroen reports about his remarkable 2018 field season:
I study how rising temperatures may affect the reproductive success of Sanderlings in Zackenberg, NE Greenland. Due to a disproportionate degree of climate warming in the Arctic, shorebirds that migrate to the Arctic to breed are strongly suspected to be negatively affected by ongoing climate change. Niels Martin Schmidt and his team have indeed established that the summer temperatures in Zackenberg have steadily increased during the last decades.
The expected consequence of the warming Arctic summers are a mismatch in timing between arthropods (think insects and spiders), and their shorebird predators. Indeed, the emergence of crawly creatures in the pitfall traps in Zackenberg has advanced in the last two decades, but I learned that Sanderlings in Zackenberg did not adjust the timing of their incubation. Puzzling.
So to further study the ecological interactions between Sanderlings and their prey (and the predators of Sanderling eggs such as Arctic foxes), this summer of 2018 I visited Zackenberg for the 13th time. It turned out to be an exceptional season…
Snow, very much snow!
Sanderlings and other Arctic shorebirds start laying eggs when the snow melts, which usually happens in the first weeks after their arrival, around late May or early June. Shorebirds are so-called income breeders, which means that females produce their eggs from locally acquired food. Their food appears only as soon as the tundra soil becomes snow-free.
Snow melts quicker with higher summer temperatures but it’s not that straight forward because climate models also predict that the amount of winter precipitation (i.e. snow fall) will increase. If that is true, more snow may counteract the effects of warming summers on the timing of emerging of arthropods.
Before I migrated north to follow the Sanderlings, my Danish colleagues who were in Zackenberg since early June had already reported that there was a lot of snow on the tundra and warned me that I should prepare myself for a late breeding season. On satellite images of mid-June 2018 the tundra surface was close to 100% covered in snow, and not only in Zackenberg but in the entire Northeast Greenland national park. After a delay of two days due to fog in Zackenberg in which the small chartered planes cannot land, I arrived in Zackenberg on 14 June.
In the last two weeks of June usually most Sanderling are on their nest while some late breeders, or birds whose first clutches fell victim to egg predators, can be found singing or foraging in pairs while the females gather insects to produce eggs. But not this year…
The amount of snow was so extensive, that the majority of the shorebirds in the Zackenberg valley had flocked together in the snow-free area around the field station. Very lean birds were walking between the wooden buildings in the research station and could be approached up to a few meters, probably because they were not willing to spend their last energy and the much needed time to forage on escaping from human researchers.
Catching shorebirds within the research station
It was clear that no shorebirds were going to nest within the next few weeks, if at all this summer. This exceptional situation gave me the opportunity to document the effects of the large amounts of snow on the behavior of shorebirds and their condition.
Usually, food left-overs from the station’s kitchen are discarded via a hose into the nearby Zackenberg river, such that its smell will not attract Polar Bears to the station. However, the river also only started running on 20 June, which is 16 days later than the average date in 1998-2017; a new record. The researchers were forced to get rid of the grinded food remains onto the tundra close to the station. Luckily, it did not attract Polar Bears, but it did attract a flock of several tens of shorebirds, mainly Sanderlings, Turnstones and Red Knots.
This gave me and my Danish colleague Jannik Hansen (Aarhus University) the possibility to catch birds and assess their body condition. We managed to catch 31 Sanderlings, 23 Turnstones and 12 Red Knots. Several birds were recaptured 1-3 times within a few days.
All individuals were in poor condition. Sanderlings weighed on average 44 grams (range: 33.6-54.6 grams). In comparison, Sanderlings in winter in the Netherlands weigh between 50-55 grams and incubating Sanderlings weigh on average 57 grams. It is good to realize that the incubating females have already produced a four-egg clutch weighing ca. 48 grams before they start incubation!
The locally colour-ringed birds were resighted daily near the sewage outlet and between the station buildings near snow edges. I daily woke up and went to bed with sightings of colour-ringed birds just a few meters from my bedroom window. The food waste close to the station was probably a unique opportunity for shorebirds, as there is only one village and a handful of stations in entire NE Greenland. The body masses of recaptured Sanderlings showed that they could maintain or even increase their body mass. But not all of them.
I found two dead Sanderlings near the station who seemed to have starved to death. One of them weighed 34 grams at first capture and only 32.6 grams when recaptured a few days later. It was found without head, weighing 26 grams. The other, un-ringed but intact, Sanderling weighed 31.8 grams which indicates that many of the Sanderlings were in very poor condition, indeed.
I was delighted with the recapture of a Sanderling which I ringed in Zackenberg as a 7–day old chick on 14 July 2012 and was now almost 6 years old. Luckily, with a weight of 54 grams, she was among the few birds in a good condition.
The sewage near the station did not only attract hungry shorebirds, but also served as a feeding tray for the local Gyrfalcons. Jannik and I almost daily observed one of these large white falcons hunting shorebirds, often flying only a few meters over our heads! Although we did not witness a successful attack, prey remains and plucked feathers in the vicinity of the station indicated that either the Gyrfalcon or possibly Arctic foxes were preying on the starving shorebirds.
A non-breeding year?
During the two-week period that I was in Zackenberg, I did not hear a single singing Sanderling and only a few times I heard a singing Red Knot or Dunlin. I observed two Sanderling pairs, which however seemed to have broken up, or at least could not be found again, during the following days.
Also surprisingly few Sanderlings that were locally colour-ringed were observed. Because Sanderlings are very site faithful to their breeding territories, and given that the snow conditions were similar in the whole range of northeast Greenland, I think that the majority of Sanderlings never arrived in Zackenberg but stayed in more southerly regions with better feeding possibilities.
In recent years, Sanderling hatch dates in Zackenberg ranged between 27 June and 30 July (average 12 July). With an incubation duration of 22 days and four days to lay the clutch of four eggs, this implies that Sanderlings usually start laying around 16 June and at the very latest at 4 July. Given that on 27 June all of the Sanderling habitat in the Zackenberg valley was still covered under at least a meter of snow, it is very unlikely that Sanderlings and other shorebirds will breed this year in Zackenberg, or even entire Northeast Greenland.
Request to report the proportion of juvenile Sanderlings within flocks
What are the consequences of a non-breeding season for the Sanderling population? This will depend on the scale at which the snow cover has affected Sanderling reproduction. The Sanderling breeding area is larger than northeast Greenland only, and it is possible that outside the area affected by snow, Sanderling reproduction will be good this year.
I ask for your help to document the effect of snow conditions on Sanderling reproduction and to score the number of juvenile Sanderlings within flocks at your local beaches. I prefer you to repeatedly observe and score the percentage of juvenile birds in the same area between August and November, following a standardised protocol. You can find more information in the manual which can be downloaded below. Download the Sanderling Ageing Manual here.
Klaassen, M., Lindström, Å., Meltofte, H. & Piersma, T. (2001) Arctic waders are not capital breeders. Nature, 413, 794.
Reneerkens, J., Schmidt, N.M., Gilg, O., Hansen, J., Hansen, L.H., Moreau, J. & Piersma, T. (2016) Effects of food abundance and early clutch predation on reproductive timing in a high Arctic shorebird exposed to advancements in arthropod abundance. Ecology and Evolution, 6, 7375–7386.
Reneerkens, J., van Veelen, P., van der Velde, M., Luttikhuizen, P. & Piersma, T. (2014) Within-population variation in mating system and parental care patterns in the sanderling (Calidris alba) in northeast Greenland. The Auk: Ornithological Advances, 131, 235–247.
Schmidt, N.M., Mosbacher, J.B., Nielsen, P.S., Rasmussen, C., Høye, T.T. & Roslin, T. (2016) An ecological function in crisis? The temporal overlap between plant flowering and pollinator function shrinks as the Arctic warms. Ecography, 39, 1250–1252.
Professor Theunis Piersma, of the University of Groningen and of the NIOZ Royal Netherlands Institute for Sea Research, has been awarded the prestigious Marsh Award for International Ornithology by the British Trust for Ornithology (BTO). The award, which is presented annually, is given to an individual scientist whose work on the international stage has had a significant influence on British ornithology. This year, the Marsh Award for International Ornithology has been awarded to Professor Theunis Piersma in recognition of his scientific work on migration, ecology and evolution of birds and other taxa.
Using Red Knots and Black-tailed Godwits as the maina study species, Theunis and his group established a framework to predict the physical attributes and behaviour of individuals based on climatic, disease and food related factors. His work as also focused on the evolutionary trade-offs involved in predation and anti-predatory behaviour across different species along the food chain. This work, in particular, holds high policy-relevance, as it informs on the risk of overexploitation of marine areas as well as our countryside.
Professor Piersma was also one of the driving forces in establishing the Global Flyway Network, which focuses on long-term demographic studies of shorebirds to identify natural selection pressures on this beleaguered group of birds.
Dr Daria Dadam, BTO, said, “Theunis is a very worthy recipient of the Marsh Award for International Ornithology. His work on shorebirds has revolutionised the way we think about how these birds interact with the habitats they live and feed in. Without this we would have a much poorer understanding of just how important our marine areas are for them, and how even small changes can have consequences for these global travellers.”
Professor Theunis Piersma, said, “The Marsh Award is a fantastic recognition of what we have been trying to achieve as an international team, carefully deciphering the ecological factors determining their distributions and numbers, what these epic migrants have to say about the state our shared world. As deeply amazing the shorebirds are in their own right, they also have a role for us to play as the canaries in the global coal-mine.”
As well as a leading academic, he is also a dedicated mentor to the younger generation of scientists. He has supervised 50 PhD students and 20 postdocs, and he and his team hosts visiting students and scientists from all over the World.
Marsh Award for International Ornithology is run in partnership with the British Trust for Ornithology (BTO) and recognises an individual scientist whose work on the international stage has had significant influence on British ornithology, especially as reflected in the work of BTO scientists and volunteers.
Curious to understand more about oversummering waders in West Africa, we set out to count our study areas in Parc National Banc d’Arguin, Mauritania.
During counts between 9 and 15 July 2017, carried out by the GFN team consisting of Ahmed Medou, Ahmed Amarajeyat, Mohamed Camara, Jan van Dijk and Bob Loos, a total of almost 65,000 birds were counted at six sites near Iwik, Mauritania (see map).
During high tides, the islands of Arel, Nair and Zira were counted, together with the coast of Ebelk d’Aiznaya and part of the Baie d’Aoutief.
The highest numbers were recorded for Flamingo (13,800), Curlew Sandpiper (12,614!), Dunlin (7,758) and Bar-tailed Godwit (5,046). Surprisingly, only 1,357 Red Knots were counted.
The last census of oversummering waders in Banc d’Arguin dates back to June 1988 when the entire area was counted between 8 June and 3 July during a WIWO expedition.
Comparison of the results with 1988 is not yet possible because the results per counting area from 1988 are not yet available. However we know that in June 1988 on Arel 2,400 Sanderlings and 1,400 Curlew Sandpipers were counted. We arrived at 2,450 Sanderling, and a spectacular number of more than 10,000 Curlew Sandpipers!
As expected, the majority of the oversummering waders were “young” birds, born in the previous summer and now in their second calendar year.
We also collected more than 300 colour-ring re-sightings from, among others, Red Knots, Bar-tailed Godwits, Curlew Sandpipers, Whimbrels and Spoonbills (both the local breeding birds of the subspecies balsacii and birds from the Dutch breeding population that decided to oversummer). More about those birds next time!
For curious readers we included the count data below.
Emma Penning reports that currently (1 August 2017) over 21,000 Sanderlings roost on the Wadden Sea islet Griend, on sand banks actively created to allow Griend to “wander” again. This is twice the Dutch wintering population (ca. 9,000), and as high as the British wintering population of 20,500 birds (Reneerkens et al. 2009). As much as 10.5% of the flyway population is now on Griend (van Roomen et al. 2015). A record number of Sanderling on a single roost!
Emma Penning from the Royal NIOZ, and a team of researchers of the University of Groningen and NIOZ, are currently working on the island to document the ecological and geomorphological consequences of the ‘Griend Repair project’ by the owner and manager Natuurmonumenten.
Griend is a small uninhabited island in the middle of the Dutch Wadden Sea. Natural erosion processes would make this type of islet “wander” through the Wadden Sea, but the protecting sand dyke created decades ago had washed away. In the summer of 2016, sand and shells have been resupplied so that natural processes can take their course again. At the same time vegetation cover on the island has been removed to ensure breeding habitat for terns and gulls. The new very low and 400 m wide sand bank protects against erosion from the west, and “feeds” the island with sand to stimulate growth at the north and south sides. This sand bar apparently is an attractive feature for Sanderling.
To investigate the effects of the recovery project, and to find out more about the natural functioning of this Wadden Sea island, an intensive four-year research project has started that will run until 2020. Tracking and tracing the movements of Sanderlings and documenting their diet is part of the program.
Already before the restoration, Griend was a central hub for Sanderlings foraging on the mudflats of the western Dutch Wadden Sea. We expected that they would continue to roost on Griend after the restoration, because the barren and open character of the new sand bank Griend would offer a safe place for Sanderlings. But this turn-out of >21,000 birds is more than we dared to hope for! Our brand new tracking data shows that indeed they use a variety of feeding locations throughout western Wadden Sea. More on that later.
Reneerkens, J., Benhoussa, A., Boland, H., Collier, M., Grond, K., Günther, K., Hallgrimsson, G.T., Hansen, J., Meissner, W., de Meulenaer, B., Ntiamoa-Baidu, Y., Piersma, T., Poot, M., van Roomen, M., Summers, R.W., Tomkovich, P.S. & Underhill, L.G. 2009. Sanderlings using African–Eurasian flyways: a review of current knowledge. Wader Study Group Bull. 116: 2–20.
van Roomen M., Nagy S., Foppen R., Dodman T., Citegetse G. & Ndiaye A. 2015. Status of coastal waterbird populations in the East Atlantic Flyway. With special attention to flyway populations making use of the Wadden Sea. Programme Rich Wadden Sea, Leeuwarden, The Netherlands, Sovon, Nijmegen, The Netherlands, Wetlands International, Wageningen, The Netherlands, BirdLife International, Cambridge, United Kingdom &, Common Wadden Sea Secretariat, Wilhelmshaven, Germany.
Today (17 April 2017, 7:00 and 8:45) from the seabird migration observation point at Westerslag on the island Texel (Netherlands) we observed 425 Bar-tailed Godwits migrating northward. The groups of 40-60 birds each flew against an adverse northern wind (4B).
Remarkably, on the previous day (same time, same spot) not a single migrating Bar-tailed Godwit has been seen! The wind was quite the same: NW (4B).
In the Mokbaai at the southeast point of the island Texel at high tide at least 96 resting Bar-tailed Godwits were observed today, whereas on the 15th only three birds were present.
Along Egmond aan Zee, another seabird migration observation point, in period of three hours no less than 2428 Bar-tailed Godwits got through in northern direction. All birds are presumed to be the subspecies taymyrensis, who winter in Africa mainly Mauritania, and use the Wadden Sea as staging site. They will stay here close to one month, to recuperate before they migrate to their breeding grounds in Siberia.
The West African-Siberian Connection, in which the Wadden Sea plays a vital part as necessary stepping-stone between wintering- and breeding grounds, a distance of approx. 8,000 kilometres!
And now we are waiting for the first sat-tagged bird returning to the Wadden Sea!!