Category: BeBirds

The sudden apparition of Bewick’s Swans in the Evros Delta is puzzling. It is quite a rare event to see a species colonizing a new area so quickly and in such a number. Because we are curious and want to be sure that their future in the area – and beyond – will be preserved, it raises some essential questions:

From where are they coming from, in other words what’s their breeding origin ?

What factor(s) made(s) possible that they have arrived up to the Evros Delta ? Do they were forced to leave from another place ?

What route(s) did they follow to reach Greece ?

What characteristic(s) of the Evros Delta made(s) possible for thousands of Bewick’s Swans to spend safely the winter in Greece ? Are these characteristics adequately integrated in the management plan of the Evros Delta National Park? We need to be sure that the swans will benefit of the ideal condition for many more years.

Let’s begin by the beginning… The migration route.

What do we know already ? We have 2 sources of information: the observation of migrating Bewick’s Swans and the results of ringing. No way concerning the observations, the max number of Bewick’s Swan seen simultaneously in Romania is probably 100, the same for Bulgaria and almost 300 for Ukraine. It seems improbable that thousands of migrating swans have escaped the attention of local ornithologists. But it is not impossible because it is known that Bewick’s Swan are able to fly non-stop up to 2000 km.

Checking the ring recovery database of the Bird Ringing Centre of Russia gives some information regarding a route to Greece.

The data show a strong migration route from the breeding grounds in the tundra of western Siberia to the direction of the well-known wintering grounds situated mainly on the southern North Sea area. The Russian database reports also some movements to the south south-east with one ring recovery in the area of Perm on the west of Ural then another along the Volga between Volgograd and Astrakhan and a third to the Kraï of Stavropol at equidistance between the Caspian and Black Sea. This last location is situated 1400 km east of the Evros Delta.

Further to these finding of dead swans, three visual sightings of marked Bewick’s Swans were made so far during the surveys conducted in the Evros Delta. It concerns swans that were fitted with a coloured neck collar engraved with an unique code allowing individual identification at distance. The first sighting dated 04/02/1997 and concern thus one of the very few Bewick’s observed in the Evros Delta. It was ringed at 3558 km distance in the Pechora delta on 15/08/1992 (see blog 23/11/2015). A second Bewick’s Swan with a neck collar was observed also on Paloukia Lagoon on 06/12/1998. It was ringed by Dutch ornithologists on 27/11/1994 in the Flevoland Polder in the central Netherlands. The distance between both locations is 2004 km. The last neck-collared Swan observed in the Evros Delta was also marked in the Netherlands, in Wieringermeer on 16/12/2006. It was seen in Greece on 18/02/2010.

But very interestingly it was observed earlier in the same winter along the Baltic Sea by the celebrated swan’s specialist of Latvia Dmitrijs Boiko. That particular Bewick’s Swan was thus going to Greece throughout Eastern Europe. Notably that same swan was wintering previously in Welney, Norfolk (United-Kingdom). It was back in the same place the next winter after having visited the Evros Delta, then it was seen the next winter in The Netherlands. It indicates that at least some Bewick’s Swans are able to change regularly of wintering ground.

All these data leads us to one conclusion: we have to investigate further the migration route of the Bewick Swan’s wintering in Greece! Because it seems currently difficult to attempt catching Bewick’s in the Evros Delta without major disturbance let’s go to take the problem by the other way and organize an expedition to the tundra of Russia to tag swans during the summer.

Thanks to Emil Todorov (Societatea Ornitologica Romana) and Boris Nikolov Nikolov (Bulgarian Ornithological Centre, Institute of Biodiversity and Ecosystem Research) for having provided information regarding Bewick’s Swan occurrence in respectively Romania and Bulgaria. The Bird Ringing Centre of Russia is part of the Severtsov Institute of Ecology and Evolution. Reports of neck-collared Bewick’s Swan are managed by the observation platform www.geese.org.

Paloukia lagoon, 04/02/1997 10:45, 25 Bewick’s Swans including a brood of 4 cygnets are resting on the ice. They are found during a survey aiming to search for Slender-biller-Curlews Numenius tenuirostris a much threatened wader species. Extraordinarily, one adult is marked with a blue neck collar inscribed with a 4 digits code. It allows to determine that it comes from the Pechora Delta, on the Siberian breeding grounds. It was marked on 15/08/1992 by a joined team of Russian and Dutch ornithologists.

George Handrinos and Filios Akriotis report in their opus “The Birds of Greece” (Ch. Helm, 1997) eight previous records of the Bewick’s Swan in the country. The first was in 1934 in Kavala, others were in the Evros Delta (3 records), Kerkini (3 records) and Kastoria Lake (1 record). The grand total of individuals is 21 with a maximum flock size of 6.

Since the winter 1996-1997 at least, the Bewick’s Swan is an annual winter visitor in the Evros Delta. The increase is regular, almost 500 ind. are counted during winter 2005-2006, 800 in 2008-2009. The numbers explodes during next winter with 2250 Bewick’s Swans counted simultaneously. During winters 2013-14 and 2014-2015, the flock is estimated at 4500 individuals. A spectacle not to forget! Moreover many thousands of Mute Swans originating from Ukraine and southern Russia and Whooper Swans of unknown origin are wintering in the Evros Delta at the same time. On 28/01/2015 it is not less that 10.800 swans of three species that are counted on the lagoons of the Evros Delta! Probably an European record.

The wintering of Bewick’s Swans in the Evros is closely surveyed and a Russian ornithologist working on the shores of the Arctic Ocean was also coming to the delta to track the swans up to the Mediterranean.

The Evros Delta is a unique place in the Mediterranean with a very diverse biodiversity. It is a National Park worth to paid a visit. A dedicated team of environmentalists, ornithologists and wardens monitor the site and assure its preservation. You are looking for a field trip for the next holidays? See here!

The Bewick’s Swan Cygnus bewickii is a breeding endemic of the tundra of Russia. It means that it is only breeding in this part of the World.

It is easily distinguished from the Mute Swan Cygnus olor by its yellow and black bill and a much smaller size.

The Mute Swan is typical with orange on the bill (photo Didier Vangeluwe).

To tell the difference between a Bewick’s and a Whooper Swan Cygnus cygnus – the third swan species of Eurasia – is much less straightforward! The Whooper has also yellow on the bill but more extensively, it is of greater size and is may be best detected by its long, very long neck with a powerful bill and head. Side to side, the Bewick’s is delicate and slender. The voice could also help to identification. The Mute Swan is … mute but gives a very particular noise with its wings when flying. Both Bewick’s and Whooper are very vocal, frequently calling a “whoop-whoop-whoop” deeper and stronger with a second syllable higher for the Whooper compared to those of the Bewick’s .

The long and triangular bill with a large proportion of yellow is typical of the Whooper Swan (photo Didier Vangeluwe).

Weather conditions prevailing during the winter in the tundra does not allow an herbivorous bird like the Bewick’s Swan to stay all-year round close to its breeding site. It is a long distance migratory species. But not all Bewick’s are wintering in the same area. They are actually 3 distinct zones, one centred on the North Sea, another in South East China and Japan and a third on the southern shores of the Caspian Sea.

Three wintering zones? Really? No! Since 1997, a new wintering zone has been established in Greece, in the Evros Delta. At the cross-road of Europe, Asia and Africa, the Evros Delta is one of the most – if not the most – nature-rich coastal wetland of the Mediterranean. The flock was estimated to 4500 Bewick’s Swans during February 2015. An incredible sight! And a unusual event considering that we are the last years much more used to announce decline and extinction…

But from which breeding grounds are coming these swans? What route do they fly to connect the Arctic to the Mediterranean? What factors make possible that Bewick’s Swans have colonized a new wintering area situated minimum 2000 km from the nearest known “historical” site? Is it needed to take (management or legal) measures to assure their future in Greece?

To answer these questions is particularly important considering that in the meantime the numbers of Bewick’s Swans wintering in the North Sea area have declined by 30% during the last 15 years. A very important and worrying drop!

It is to participate to the understanding of these questions that ornithologists of the Severstov Institute of Ecology and Evolution (Bird Ringing Centre of Russia), the Goose, Swan and Duck Study Group of Northern Eurasia and the Royal Belgian Institute of Natural Sciences (BeBirds – Belgian Ringing Centre) have joined their effort, together with the Evros Delta National Park Management Authority and the Forest Research Institute of Thessaloniki to launch the program “The Odyssey of the Bewick’s Swan – another route to Greece!”

We propose to share our observations and findings with you.