Transmitter research on storks from the Zwin Nature Park

On Monday 29 June 2020, four new young white storks were equipped with transmitters in the Zwin Nature Park in Knokke-Heist. As such they follow in the footsteps of the three juvenile stork who were equipped with transmitters here in 2019, in collaboration with the Royal Belgian Institute of Natural Sciences. Thanks to the transmitters, the scientists are able to continuously monitor the storks and obtain information about the migration routes, the wintering areas and the dangers the storks face. The research also makes it possible to estimate the consequences of changing conditions during the storks’ migration and wintering.

One of the young White Storks that was equipped with a transmitter at the Zwin Nature Park in 2020, on the nest with a parent bird. 29 June 2020 © RBINS/K. Moreau

For information on the history of white storks in the Zwin Nature Park, in Belgium and in Europe, and for details on the design and technical aspects of the Belgian transmitter research, we refer to the article that was published in 2019. In this contribution the focus is on what the transmitter-storks from 2019 have taught us in the meantime, and on the continuation of the research.

Winter Adventures

The route followed by the three young Zwin-storks (Emily = red, Reinout = green, Hadewijch = blue) after being equipped with a transmitter on 26 June 2019 is summarised in the following animation, and commented upon in the text underneath.

After installing the transmitters, the young storks stayed in their nests for another two weeks. On 10 July the first flights were registered, the following weeks the area around the Zwin was extensively explored. The big departure took place on 21 August. The three birds departed together (no doubt in the company of other birds of the same species, but not their parents – it is known that they spend the winter in the Zwin Nature Park) and crossed France in no less than 6 days. On 30 August, meanwhile in northern Spain, they separated their ways.

  • Emily turned out to be in the biggest hurry. On September 1st she was already near Gibraltar, and on September 23rd she crossed ‘the Strait’ to Morocco. After some wandering around in the north of that country she finally settled in a fixed winter area around mid-November. But things didn’t end well for her: on 20 February she flew into a high-voltage pylon and got electrocuted.
  • Reinout, Emily’s sibling, on the other hand, was the least hurried of the trio. He stayed near Madrid until the beginning of October, before descending further to the south of Spain. And there he stayed, the winter was spent in the region of Seville. Mid-March he started his return journey, passing Belgium (where he spent one night) on 12-13 April, and then flying back and forth in the central Netherlands and the neighbouring part of Germany.
  • Hadewijch (from another nest) stayed in N-Spain until mid-September, but finally made the crossing to Africa on September 30th. There she also wandered around, to settle in a fixed area in the north of Morocco at the end of November (though another area than Emily). At the end of March 2020 she left this area again, and started heading north. After a long stop in central France (mid-April – end of May) she then flew straight back to the Zwin Nature Park, where she arrived on 3 June and is still present today.
Ooievaar Hadewijch back at the Zwin Nature Park, 8 juni 2020 © Zwin Natuur Park

Interesting Findings

So far only three storks were followed during one year, so we are talking about a small sample and have to be cautious about linking strong conclusions to the results. But there are certainly some interesting observations:

  • the three birds left together and stayed together for a considerable distance (as far as N-Spain)
  • even after the split-up, they repeatedly visited the same areas, but at different times → points towards potentially exceptional importance of certain areas
  • visits to landfill sites are a striking feature → interesting in relation to the important question of the impact of the European ban on open landfill sites (soon to be applied in the Iberian Peninsula) on species that have learned to look for food here
  • American crayfish, an introduced exotic species, are a sought-after snack in the Spanish rice fields.
  • one bird stayed in Europe, but the two that reached Africa didn’t cross the Sahara either
  • when the birds settle for the winter, the range suddenly becomes very small
  • electrocution is a real danger to large birds (confirmation)
  • young birds show a great lust for wandering and start the return journey rather late, but a return to the region of birth is already possible in the first year
White Stork, Zwin Nature Park, 29 June 2020 © RBINS/K. Moreau

Further Research

Due to the small sample and the limited time span of the investigation so far, the above findings should not yet be considered to be significant conclusions. That is why the 2019 storks are still being monitored, and on 29 June 2020 four more storks were equipped with transmitters at the Zwin Nature Park (watch the video!). This time they originate from three different nests. The intention is to further increase the number of storks in the next few years. By the way, the transmitters remained unchanged compared to 2019. They weigh only 25 grams (less than one percent of the body weight) and are very sustainable. Working on solar energy, they transmit the accurate data collected by their GPS via the GSM network. When there is no range, everything is stored in an internal memory, and transmitted when possible. And there is also communication with the transmitters in both directions, e.g. the frequency of the transmission of location details can be adjusted.

Also the traditional ringing research remains important for building insights and formulating answers to the challenge of protecting storks, and migratory birds in general. After all, it is not enough to protect migratory birds in their breeding areas, this is also necessary in the winter quarters and along the entire migration route.

The results of the research can be followed on the website of the Zwin Nature Park – Operatie Ooievaar.

Ringed White Stork, Zwin Nature Park, 29 June 2020 © RBINS/K. Moreau

Names for the Storks

We are still looking for names for the four newly-equipped storks. Proposals can be submitted until 10 July, accompanied by a short justification for the proposed names. On 15 July the chosen names will be announced.

Interesting to know is that the sex of storks is almost impossible to determine externally. Only during mating can it be seen with certainty which position is taken by the two partners. Therefore, the sex of the young birds from 2019 is not yet known. It is quite possible that Reinout is the only female, and that the names Emily and Hadewijch were assigned to males. Maybe choose gender-neutral names? For the birds from 2020, however, the sex will soon be known, as some feathers have been collected for DNA analysis.

As an international airport for birds, the Zwin Nature Park is a knowledge and expertise centre for bird migration. In addition to ringing storks and installing transmitters, the Zwin Nature Park also focuses on ringing of other bird species. From 1 August to 7 November 2020, ringing will take place almost every day, and the public will also be able to observe this activity. In Belgium, the scientific ringing of birds is coordinated by the BeBIRDS group of the Royal Belgian Institute of Natural Sciences (RBINS).

RBINS and Zwin Nature Park install GPS transmitters on white storks

In the Zwin Nature Park in Knokke-Heist three young storks were provided with a transmitter at the end of June. Thanks to their transmitters, the movements of these storks can be followed at all times. With this study, the Royal Belgian Institute for Natural Sciences and the Zwin Nature Park want to document the consequences of changing conditions in the wintering areas on the migration behaviour of the storks.

Young white stork that was equipped with a transmitter at the end of June 2019 at the Zwin Nature Park. (© Zwin Natuur Park)

Since Leon Lippens started an introduction programme for white storks Ciconia ciconia in the Zwin Nature Park in 1957, about five hundred young have hatched here (the first in 1965). More than 300 of them were equipped with a scientific ring, within the framework of the long-term research tradition and cooperation with the Royal Belgian Institute of Natural Sciences. The majority were reported at least once (on average five times per reported stork), mainly along an axis towards the southwest, through the western half of France and central Spain. The furthest observation of a Zwin-ooievaar came from Algeria, at 2,164 kilometres from the Zwin. But Belgian storks have also been reported to spend the winter in West Africa, south to Senegal and Mali. The white stork is one of the species for which the Zwin has been designated as a special protection area under the EU Birds Directive.

Reports of white storks that were ringed in Belgium, 1965-2019 (© RBINS/Geoapp BeBIRDS)

This year the Zwin population counted 13 breeding pairs. In the wider area, however, 27 additional pairs were documented (region Knokke-Heist, Damme, Bruges, and across the Dutch border), so that the total regional population in 2019 was no less than 40 breeding pairs. A few years ago, the feeding of storks in the Zwin was stopped, which probably contributed to their distribution over a larger area.

Transmitters in addition to rings

In 2019, the Zwin also devoted attention to the ringing of a number of young storks: on 5 June, 13 individuals were provided with a scientific ring. The codes on these rings can be read remotely with a pair of binoculars or a telescope, but the chance that a ringed stork is observed and reported remains rather small. Although such observations teach us a lot, they are still snapshots. With a transmitter, a bird can be tracked continuously, which provides much more information about the survival, the movements and the habitat use of the transmitter-equipped birds.

The transmitters only weigh 25 grams and use solar energy (© Zwin Natuur Park)

On 26 June, for the first time, three young Zwin storks (from two nests) were equipped with a transmitter. They weigh only 25 grams, which represents less than one percent of the weight of the birds. The transmitters are very sustainable: they operate on solar energy and transmit the data that their GPS collects via the GSM network. Don’t worry if there is no reception: everything is stored in the internal memory and passed on when a signal is available. It is also possible to adjust the transmitter parameters (such as the frequency of location measurements) remotely. The accuracy is astonishing, positions are determined to within a few meters.

The spatial use of one of the young storks that carries a transmitter (period 20-28 July, the bird is hanging around the nest site) shows a very high resolution (© RBINS/Geoapp BeBIRDS)

Storks on garbage dumps

Before 1990, almost all Western European storks crossed the Strait of Gibraltar (the strait that separates Spain from Morocco) in the autumn to spend the winter in West Africa. Since then, however, much has changed. More and more storks have understood that they could drastically shorten this long and energy-consuming journey by staying in Spain, where they find all the food they need on landfills. In the winter of 2018-2019, up to 46,000 wintering storks were counted on the Iberian Peninsula. This is no less than 20% of the Western European population. These birds also have a higher chance of survival, and return more quickly to the breeding grounds in the spring, where they can occupy the best territories.

The storks experience no problems with the transmitters on their backs (© K. Moreau/RBINS)

But … clouds are rising in the Spanish stork paradise skies! The European Waste Framework Directive prohibits landfills exposed to the open air, and the European Commission took Spain to the European Court of Justice in June 2018, in response to repeated calls for this legislation to be applied in Spain. The Spanish garbage dumps that many storks have learned to use will therefore be closed shortly. This will fundamentally change the state and conditions of their wintering quarters. The RBINS and the Zwin Nature Park are therefore seeking to use the transmitters to help document the impact of this changing situation in Spain on the storks’ migratory behaviour.

Two young storks with transmitters in the ‘Kleine Vlakte’ outside the Zwin Nature Park (© K. Moreau/RBINS)

The results of the research will be available on a specific project page on the website of the Zwin Natuur Park. It is the intention that more storks will be equipped with a transmitter in the coming years.

As an international airport for birds, the Zwin Nature Park is a knowledge and expertise centre for bird migration. In addition to ringing storks and installing transmitters, the Zwin Nature Park also focuses on ringing of other bird species. From 1 August to 20 October 2019, ringing will take place almost every day, and the public will also be able to gain an insight into this activity. In Belgium, the scientific ringing of birds is coordinated by the BeBIRDS group of the Royal Belgian Institute of Natural Sciences (RBINS).

Back to the North !

The first two Bewick’s Swans equipped with a GPS tag during past summer in the tundra of Yamal but at the same site a few days apart, have very recently left their wintering site separated one of the other by … 8000 km!

The first to take the northern route is the adult female 832X. She left Poyang Lake area (southeast China) on 03/03/2016. She had arrived in the region on 25/11/2015 and has successively visited the Sai Hu lakes, Longhu and Longgan lakes. So she stayed a total 99 days near the Yangtze River before resuming her migration back to the north.

Cygnes de Bewick hivernat dans la région du Lac Poyang, 29/11/2014 (photo Didier Vangeluwe)
Bewick’s Swans wintering in the Poyang Lake region, 29/11/2014 (photo Didier Vangeluwe).

Between 03/03/2016 and 07/03/2016, 832X has traveled 1400 km to the north-northeast with a maximum peak of 215 km in 3 hours. Since she is in halt on the Yellow River in the district of Donghan, 250 km from the border with Mongolia. This is exactly where 865X, another Bewick’s Swan from Yamal having wintered in the Yangtze region, had stopped in last autumn migration.

The second Bewick who started the spring migration is 854X. It is a second-winter male that had (after years of questions !) indicated us the route to the Evros Delta. 854X had arrived in the Evros on 12/12/2015.

Zone d'hivernage du Cygne de Bewick 854X dans le Delta de l'Evros, à la frontière entre la Grèce et la Turquie.
Wintering area between 12/012/2015 – 07/03/2016 of Bewick’s Swan 854X in the Evros Delta at the border between Greece and Turkey.

After 86 days of back and forth between Greece and Turkey, the Evros river making the border between the two countries, 854X flew in the late afternoon of 07/03/2016, heading northeast. In a step of 12 hours of continuous flight and a peak of 265 km traveled in 3 hours, 854X flew over the Black Sea in almost straight line to land on the morning of 08/03/2016 in the Nature Reserve of Chernomorsky, just east of the Bay of Tendra, Ukraine.

Twelve hours later, 854X set off again, this time eastward, for a flight of three hours maximum. At nightfall, he landed at sea, a few km off the Gulf of Khorli, a site where gather in the summer thousands of Mute Swans in flightless moult.

Les golfes de Khorli accueillent en été plusieurs milleirs de Cygnes tuberculés en mue flightless (photo Didier Vangeluwe).
The Gulf of Khorli hosts during the summer thousands of Mute Swans in flightless moult, 01/08/2009 (photo Didier Vangeluwe).

The GPS positions received suggests that during the night, 854X drifted 11 km towards the east. At dawn on 09/03/2016, he took off for a short 90 km flight which led he to the impressive hyper saline lagoons of Sivash, north of Crimea. He stayed there four days and was located several times in cropland area close to water bodies. Most likely he was feeding there.

Les lagunes hyper salines de Sivash sont un site de halte primordial des limicoles en migration prénuptiale, (photo Didier Vangeluwe).
854X has stopped from 09/03/2016 until 13/03/2013 in the hyper saline lagoons of Sivash. These lagoons are key staging areas for shorebirds during spring migration, 26/07/2008 (photo Didier Vangeluwe).

854X then resumed flight to the east for about 40 km. New stop at night, but this time on Sea of ​​Azov. And new drift during the night, up to 24 km from the coast this time. This morning, 14/03/2016, 854X resumed its journey shortly after 05:00 am (local time) always towards the east. Six hours later he was located 290 km to the east, probably when flying. 854X was then close to Beisug liman where he has stopped 51 days during post-breeding migration 2015, prior to arrive in the Evros Delta. Will he halt there again or will he continue his journey eastward to Russia and Kazakhstan?

To be continued !

Bewick ‘s Swan with yellow neckband and Lesser white-fronted Geese

February 10, 6:50, like every morning watching the swan roost begins at sunrise. Thousands of swans, mainly Bewick, gathered to spend the night safely in the marshes of Dimitriades. The flock lies on 1 km; this is a very impressive sight!

The roosting flock extends on 1 km, 03/02/2016 (photo Didier Vangeluwe).
The roosting flock extends on 1 km, 03/02/2016 (photo Didier Vangeluwe).

Most swans are swimming in shallow water, a minority is standing on the flooded mudflats. The contacts are intense, swans are very social birds outside the breeding season. They constantly vocalize. Their calls are very melodious and reach their climax when taking off. Flocks follow each other at regular interval.

8:03, two families of Bewick’s Swans take flight from the southwest corner of the roost. In doing so, they give off the view to another small group. He’s there ! The Bewick’s Swan with the yellow neckband observed there 5 days ago. But at the time the code could not be read. It makes a lot less windy today and the distance is only 400 m. It will works! After a few minutes of scrutinizing with the telescope at 70x zoom, the 4-characters code appears. No more doubts, it’s a Bewick’s Swan ringed in the Netherlands. Encoding the code on platform that compiles data from swans and geese tagging programs in Europe allows to immediately know its origin. That swan was marked on 26/12/2014 in Noord Brabant, near the city of s’Hertogenbosch. He quickly left the area to continue its wintering in Belgium, 50 km south-west, in the north of the province of Antwerp where he remained until 01/03/2015. He will then be observed on 31/03/2015 in Lithuania, when migrating to Siberia. And next winter he is now in Greece.

The Bewick's Swan with yellow nexkband marked on 26/12/2014 in the Netherlands, 10/028/2016 (photo Didier Vangeluwe).
The code of the yellow neckband was read today. It was marked on 26/12/2014 in the Netherlands, 10/02/2016 (photo Didier Vangeluwe).

This is the third Bewick’s Swan ringed in the Netherlands we are seeing in the Evros Delta. The previous was on 19/02/2010. Is this a new indication of the fact that the Bewick’s Swans traditionally wintering in this country are now deserting it ? But if that’s the case (3 observations do not allow to draw conclusions) why such a phenomenon? What happens in the Netherlands making that the country is no more favoured by the Bewick’s Swans ? Obviously, no one knows for sure.

Next objective of the day : search for Lesser white-fronted Geese, another species in decline which also winters in the Evros Delta.

A Lesser white-fronted Goose wintering among the Greater white-fronted Geese, 11/02/2016 (photo Didier Vangeluwe).
A Lesser white-fronted Goose wintering in the Evros Delta among Greater white-fronted Geese, 11/02/2016 (photo Didier Vangeluwe).

Ornithologists of the Forest Research Institute of Thessaloniki, a partner to the program on Bewick’s Swan, study their diet by analyzing the cell fragments of plants, extracted from droppings collected in the marsh Dimitriades. What a program!

The foraging sites of 854X

09/02/2016, the objective of the day: to identify the characteristics of the foraging sites of 854X, the Bewick’s Swan “sentinel” equipped with a GPS transmitter in Siberia.

The data transmitted from the arrival of the swan in the Delta of Evros indicate that it forage exclusively in the Turkish part of the Delta. The reason is simple: this area is covered by 99% of rice fields. Natural habitats, which contribute to the exceptional biodiversity of the Greek part of the Delta, were completely destroyed on the Turkish side. It is striking to observe a satellite map: east of the river, everything is a deep green: it is the rice fields. While to the west, a patchwork of colors of various shapes and sizes can be observed. There are obviously areas that are cultivated on the Greek part but not intensely while in coastal areas, salt marshes and lagoons stretch out of sight.

Satellite vieuw of the Evros Delta. The border between the Greece and Turkey follow the stream.
Satellite view of the Evros Delta. The border between Greece and Turkey follows the course of the stream. Monoculture of rice fields is widesread on the Turkish part of the Delta.

Let’s go to Turkey. A part of the rice fields is completely dry, the stubbles left after harvest line up in endless furrows. Another part is partially flooded, the bottom of the grooves being filled with water probably consecutively to the rains of the past week. A third part is completely under water, forming lakes of several km². It is on these flooded fields that gathers the majority of swans. Part of the area cannot yet be surveyed because it is under military control.

Most swans are found together in 4 huge flocks of 1500 to 4000 individuals. Small groups with a few dozen to a few hundred swans are scattered here and there. The large flocks are composed of three species of swans: Mute, Bewick’s and Whooper. All are feeding on the roots of the rice plants that were planted last spring. All sites where 854X has been located, and that could be visited, are indeed flooded rice fields.

Rice stubbles in Turkey: the essential feeding grounds of Bewick's Swan wintering in the Evros Delta, 09/02/2016 (photo Didier Vangeluwe).
Rice stubbles in Turkey: the essential feeding grounds of Bewick’s Swan wintering in the Evros Delta, 09/02/2016 (photo Didier Vangeluwe).

Apart from swans, there is almost no other birds in this part of the Delta. This is probably the consequence of the disappearance of natural habitats and the development of rice monoculture. A very important hunting pressure is another explanation: at regular intervals in each rice field one may see hunting huts when gun cartridges litter the ground by the hundreds. At 14:45 in the middle of a group of 2,700 swans feeding in a flooded rice field near the village of Enes, there he is. 854X is carefully preening.

854X in sight in Turkey, 09/02/2016 (photo Didier Vangeluwe).
854X observed in feeding grounds in Turkey 09/02/2016 (photo Didier Vangeluwe).

It’s a chance because yesterday it was located 26 km north, near the village of Ipsala. There are exactly 179 days we were together at the mouth of the river Yuribey on the shores of the Arctic Ocean.

A day is not another

It freezes this Monday 8 February 2016 at the border between Europe and Turkey. The day is dedicated to count waterfowl – swans, geese, ducks, waders and gulls – and raptors wintering in the National Park of the Evros Delta. Among these have been observed today: 2 White-tailed Eagles, two Imperial Eagles, about 20 Greater spotted Eagles, sixty Common Buzzards and as many Marsh Harriers, a Peregrine Falcon, about 15 Kestrels, a dozen European Sparrowhawks. The two Rough-legged Buzzards discovered the day before yesterday were no longer found.

Deux Aigles criards posés sur un tamarix dans les marais de Dimitriades, 04/12/2005 (photo Didier Vangeluwe)
Two Great spotted Eagles perched on a tamarix thicket in the marsh of Dimitriades, 04/12/2005 (photo Didier Vangeluwe).

Bewick’s Swans are of course always under close monitoring and the follow up of the arrival to the roosts starts at 16:00 from the dyke that separates the Drana Lagoon from the marshy area of Dimitriades. When arriving 7 Mute Swans were sleepy in the middle of the flooded area where past Friday 8500 swans from three species where gathering together. No movement or so until almost 17:15 when the young Imperial Eagle observed in the morning flies over the area towards the hills of Loutros where it roosts. 17:30, arrival of the first 8 Bewick’s Swans. The following 12 arrive at 17:35. At 17:46 p.m., it’s raining Ruddy Shelducks. 17:58 p.m. a flock of 28 Bewick’s Swans comes gently to rest on the water. 18:08 p.m., it is completely dark, end of counting. The total is doing 48 Bewick’s Swans. Yesterday they were in 1240, before yesterday 1400 and Friday 8400! Have the Bewick’s Swans wintering in the Evros Delta already started their spring migration to the tundra of Siberia?

The data transmitted by the swan 854X equipped with a GPS transmitter in Yamal are helping to understand these differences. Analysis of 854X positions at 02:00 am indicates that there is more of that one swan roost in the Evros Delta. Between 12 December 2015, the date of his arrival in Greece and 12 January 2016, 854X has used 8 different roosts, 4 located in Greece and 4 in Turkey. During this first month of presence, 854X slept 23 times in Greece and 8 in Turkey. So there is clearly a different distribution of swans between the roosts and between the nights. It is unknown why exactly, but we can assume that the weather is an important factor. This is one explanation to the variations in counts.

Localisation (étoiles) des sites de dortoir du Cygne de Bewick 854X équipé d'un émetteur GPS; le point rouge indique le dortoir des marais de Dimitriades, (carte Nicolas Pierrard).
Localization (stars) of roosting sites during the period 12/12/2015-12/01/2016 for the Bewick’s Swan 854X tagged with a GPS transmitter; the red dot indicates the roost situated in the marshes of Dimitriades, (carte Nicolas Pierrard).

Another parameter explaining these disparities between the number of swans counted at Dimitriades roost is the timing of leaving foraging site at the end of the days. GPS locations of 854X and direct observations with a telescope indicate that foraging site are almost exclusively located in the Turkish part of the Delta. By the way a visit is planned in this area during the coming days.

Today 854X was still in Turkey at 19:00. Whereas it is dark at 18:10, so it arrived in the dark at the roost and has accordingly not been detected and therefore not been counted. Yesterday, 7 February, it was located at 19:00 7 km east of the roost; most likely flying. The same that today: he came to the roost in the dark and could not be recorded. Day before yesterday he was still in Turkey at 18:00 and was at the roost at 19:00. He returned earlier that day but still after or just after dark. And on 5 February, the story is already known, 854X and thousands of fellows spent all day in the roost of Dimitriades. They just have not been feeding this day. This most probably allowed the record count.

All this did not help to resight the swan with the yellow neckband observed, but not decrypted, on 5 February. It cannot more be found!

Even more Bewick swans in the Evros Delta

The weather conditions have changed rapidly in the Evros Delta, it is not infrequent. Since last night, the wind blows north northeast, gusting up to 70 km/h. It rained much all night and part of the day. The tops of the hills bordering the valley are covered with snow as the Greek side that Turkish. The temperature is around 3-4 ° C.

The data received every hour from the Bewick’s Swan 854X equipped with a GPS/GSM transmitter indicate that it has not left the roosting place this morning. It is therefore not going to feed on the other side of the valley, in Turkey, as he is doing every day since his arrival in the Delta. Is it something happened? Or will he plays, as expected, the role of “sentinel” that allows us to detect broader phenomena?

4 pm, we left for the Drana lagoon and the marshes of Dimitriades to see what happens. The track is particularly muddy, but it works. After a couple of km, the show is unique: we are facing a sea of swan! Most have their head tucked into their plumage. The others face the storm, trying to resist on their powerful legs. Some are in the water but very close to the shore to avoid being swept away by the waves. Others are dry, on the upper parts of the salt marsh. They are mostly lying to offer the least possible resistance to gusts. It is a unique spectacle, so much swans in such meteorological conditions and in such natural habitats.

Part of the record flock of Bewick's Swan observed in the Evros Delta, 05/02/2016 (photo Didier Vangeluwe).
Part of the record flock of Bewick’s Swan observed in the Evros Delta, 05/02/2016 (photo Didier Vangeluwe).

We estimate the number of Bewick’s Swans to 8400 which must be added circa 150 Whooper Swans and 50 Mute Swans. It is a new maximum for Bewick’s Swan for the site. But what happens in the Evros Delta? From where are these Bewick’s Swans coming from? From Yamal like 854X or from another places in the tundra of Siberia? Russian colleagues are particularly attentive to the problematic, the Bewick’s Swan is an endemic breeder of Russia. It focuses all the attention of the authorities and scientists in charge of the conservation of nature in the Russian Federation.

Bewick's Swan marked with a yellow neckcollar originating from the Netherlands, Dimitriades area 05/02/2016 (photo Didier Vangeluwe).
Bewick’s Swan marked with a yellow neckcollar originating from the Netherlands, Dimitriades area 05/02/2016 (photo Didier Vangeluwe).

By watching and still watching this huge flock, our attention is drawn by a swan preening despite the strong wind. He stretches his neck, smooth, or rather try to smooth his feathers. It is marked with a yellow neckband engraved with a code enabling at distance identification. It is the fourth marked Bewick’s Swan we observe in the Evros Delta. This has certainly been ringed in the Netherlands by colleagues from the Netherlands Institute of Ecology. Despite our best efforts, we didn’t managed to read the code: it was not possible to come closer than 750 m, the light was fading to quick with the night falls, the wind vibrates the telescopes. We’ll be back tomorrow to try to find him !

The Incredible Evros Delta

5100, 5300, maybe even 6000! That’s the number of Bewick’s Swans counted the last days by the ornithologists working for the Evros Delta National Park. The previous record was set around 4500 individuals seen during the previous winter. The number of Bewick’s Swans wintering in Greece is therefore still growing while at the same time the flocks observed in traditional areas in the area of the North Sea are at their lowest.

Bewick's Swans leaving their rootst situated nearby the Drana Lagoon in Evros Delta, 02/02/2016 (photo Didier Vangeluwe)
Bewick’s Swans leaving their roost situated nearby Drana Lagoon in the Evros Delta, 02/02/2016 (photo Didier Vangeluwe).

This is not an easy task to count the swans in the Evros. Indeed, the Delta is shared between Greece and Turkey, making it difficult to carry out coordinated counts; there is also no local team of ornithologists on the Turkish side. Part of the delta is also under military control and therefore can be visited only occasionally and under strictly controlled conditions. In addition, the area of presence of swans is very large, about 350 square kilometers. Moreover a part of it is inaccessible when the river flow is so important that adjacent areas to the main branch are flooded. Additionally Bewick’s Swans are not the only representatives of their genus to winter in the Evros Delta. It is also the case for thousands of Mute Swans (from the steppe – or ancient steppes – of Ukraine and South of Russia) and Whooper Swans (most likely originating from the taiga of Siberia). The counts are therefore often slow and difficult as it is essential to carefully make the distinction between the three species. But the Greek team is particularly experienced, alternating on its territory and throughout the winter, weekly day counts and every two weeks evening counts at the roosts.

Starting today, and for 10 days, the Greek and Belgian teams are joining their force to study in the Evros the behavior of swans, their distribution between the different lagoons, their demographics by determining the proportion of young and brood size. The aim is also to go to see each site where the Bewick 854X equipped with a GPS transmitter on 14/07/2015 in the tundra of Yamal ( Siberia) has been located since his arrival in the Evros Delta on 12/12/2015. That will give the possibility to accurately determine the habitats used by this ” sentinel swan” and their relative importance. Such data are very useful for the conservation of the species giving the possibility, if necessary, to propose appropriate management measures. The GPS localization of the transmitter was set at 1 hour interval from today. This will provide even more accurate data in the coming days. This procedure will be limited in time because it is obviously energy costly and could drain the solar battery.

The sun is shining in the Evros today. Daytime temperature ranges between 10-15 °C. It turns out that almost all Bewick’s Swans left Greece to forage in Turkey. Moreover it has appeared that they didn’t came back on the Greeks roosting places before sunset. We have counted barely 150 individuals arriving at roost before darkness. But the evening was not lost! At 16:48 and then at 17:11 it is in a deafening roar that two compact waves totaling 4500 Ruddy Shelducks have arrived at the same marsh just south of Drana lagoon. This happens in the Evros Delta, and at European level, only in the Evros Delta!

Some of the 4500 Ruddy Shelducks coming to sroost nearby Drana Lagoonn, 02/02/2016 (foto Didier Vangeluwe).
Some of the 4500 Ruddy Shelducks coming to roost nearby Drana Lagoon, 02/02/2016 (photo Didier Vangeluwe).

Go up tomorrow at 6:30, before sunrise, to see if the swans were indeed coming to sleep to Greece and to count them, if possible. And perhaps also to observe 854X!

A 30 % decline !

The Bewick’s Swan is really a beautiful bird. It is elegant, graceful. His social behavior is fascinating to observe. The parents care for their young for about a year, they migrate, winter together. Adult relationships are complex. They often communicate with each other with very melodious cries.

Groupe de Cygnes de Bewick dans un champ, Ede 30/12/2015.
Flock Bewick’s Swans grazing, Ede 30/12/2015 (photo Didier Vangeluwe).

They sometimes intimidates each other, opening the wings, raising the neck, chasing each other.

They alternate periods of feeding and rest. By far, in polders of Flanders or the Netherlands, they look like pure white flakes. But in the evening, invariably, they fly off in well-structured flight to join their roosting place located on a large body of water, sometimes situated dozens of kilometers from their feeding site. As much as they are (relatively) tolerant to human activities during the day, they are on their guard after the arrival of darkness seeking to protect themselves from terrestrial predators by sleeping on water.

Départ vers le dortoir, Ede 30/12/2015.
Flying to the roosting place, Ede 30/12/2015 (photo Didier Vangeluwe).

An idyllic situation? Not really. The number of Bewick’s Swans wintering in the North Sea area (from East to West in Poland, Germany, Denmark, Germany, Netherlands, Belgium and the British Isles) fell by 30% between winter 1994- 1995 and winter 2009-2010. The data of the last comprehensive count conducted a year ago (in January 2015) are not yet available. It seems that the negative trend has continued.

evolution du nombre de Cygnes de Bewick hivernant dans la région de la mer du Nord
Evolution of the numbers of Bewick’s Swans wintering in the North Sea area and in the Evros Delta (Greece).

What are the reasons for this decline that can be described as catastrophic? They are largely ignored. But several worrying facts are observed: Bewick’s Swans wintering in the North Sea are have few offsprings (cygnets) in comparison with populations wintering in China and Greece. Over the last 10 winters, the average proportion of cygnets was 10.4%. The recorded maximum was 16.6% during the winter 2012/2013 and the minimum of 4.7% (which is very little!) in winter 2007/2008. These data were collected largely through hundreds of volunteer birdwatchers who count and observe the swans each winter. Furthermore, the British ornithologists of the renowned Wildfowl & Wetland Trust made a chocking statement. Since 2000, they X-rayed 47 Bewick’s Swans during ringing operations conducted in England. Among them, 22.7% contained lead shot. This suggests that despite their status of strictly protected species in the European Union and Russia, Bewick’s Swans are still regularly poached. Finally, and here are the Dutch ornithologists from the Institute of Ecology (Wageningen) who are leading, we observe that Bewick’s Swans regularly change food in recent winters and most of these are linked to human activities: meadows, plowing beets, potatoes, corn stubble. This behavior is it indicative of an unstable situation, unfavorable to swans? Studies are underway. And then there is the arrival, gradual but fast, of thousands of Bewick ‘s Swans in the Evros Delta in Greece. Is it there a cause and effect with the decrease of Bewick’s Swans in the North Sea area? Is it a population shift? Is this a good – or bad news? It is this that try to understand the Belgian, Russian and Greek partners this program.

We must quickly understand what’s going on!

He did it !

The Bewick Swan 854X that was since 51 days in the liman of Beisug on the eastern coast of the Sea of ​​Azov (Russia) has arrived in the Delta of Evros, Greece. Incredibly, in this first year of the program, we drilled the mystery flyway who join the new Greek wintering site to the Siberian breeding grounds.

Let’s return to the events of the past days. 854X left the liman of Beisug on 10/12/2015 at about 08:00, around sunrise thus. He flies due west over the sea, through Crimea, overflying the lagoons of Sivash, reaches the Black Sea in the Bay of Karkinitsky, turns then towards the south-west along the west coast of Crimea, then rolls over straight until reaching Bulgaria via the Natura 2000 site of ​​Durankulak, a few kilometers from the border with Romania.

La zone NATURA 2000 de Durankulak est un site d'hivernage très important pour les Bernaches à cou roux, 11/02/2012 (photo Didier Vangeluwe)
The NATURA 2000 site Durankulak in Bulgarian Dobrodgea is an important wintering site for Red-breasted Goose, 11/02/2012 (photo Didier Vangeluwe).

After 40 km flying over Dobrogea, it redirects to the south, finds back the sea up to the bay of Kavarna where he lands, 300 m offshore facing holiday resorts. It is about 01:00. This first part of the journey lasted 17 hours during which 854X has traveled at least 880 km with probably only one short stop near the nature reserve (zapovednik) Lebaj in Crimea. The calculated maximum flight speed is 91.6 km/h over three hours.

854X resumes migration around 08:00 again on 11.12.2015. He is heading inland, towards the southwest, for 95 km. Around noon, he changes track course and flies towards the northeast for 45 km. It takes a new bearing around 15:00 this time towards the southeast and finally stops on a small lake around 18:00, near the city of Blagovo. He spends there the night. Clearly 854X had a problem of orientation that day. He has traveled just 200 km. But he managed to compensate and regains its course for the next morning, when he first takes to the south-southeast for 23 km and then south for 270 km. He flies over Bulgaria, a short part of Turkey and then Greece entering the country at the height of the city of Orestiada. He joins there the Evros River valley. At 15:00, on 12/12/2015, 854X is located on the lagoon of Palukia in the middle of the Evros Delta National Park.

Cygnes tuberculés et de Bewick sur la lagune de Paloukia, 06/02/2011 (photo Didier Vangeluwe)
Mute Swans and Bewick’s Swans on Palukia lagoon, 06/02/2011 (photo Didier Vangeluwe).

He left the tundra of Yamal 93 days earlier and has traveled in between some 5700 km, local movements during periods of stopover excluded. He has overfly Russia, Kazakhstan, the Ukraine, Bulgaria, Turkey and finally Greece.

Meanwhile, three other Bewick’s Swans tagged at the same time in Yamal are still on the Poyang Lake, 400 km from the coast of Sea of China and 7900 km of the Evros Delta!