Full project name: “Czynna ochrona zagrożonych gatunków awifauny wysp na obszarze OSOP Dolina Środkowej Wisły: kontynuacja” (Active conservation of threatened bird species of islands in the SPA Middle Vistula Valley: a continuation)
The project was co-funded by the European Union from the European Regional Development Fund, as part of the scheme Infrastructure and Environment (project no. POIS.05.01.00-00-325/10.00), and subsidised by the National Fund for Environmental Protection and Water Management.
Project duration: November 2011 – June 2015
The project was a continuation of earlier work, carried out jointly by the Polish Society for the Protection of Birds and the Centre for Ecological Research of the Polish Academy of Sciences. This earlier project was carried out in the Middle Vistula between Dęblin and Kozienice and its aim was active conservation of threatened species of gulls, terns and plovers. It was financed by the EkoFundusz between 2008-2010 and by the GEF/SGP Small Grants Programme between 2005-2006.
Importance of the Middle Vistula Valley for birds
The islands in the Middle Vistula Valley are nesting sites for many waders. They include species of special concern in Europe and/or Poland: the Little Tern (Sternula albifrons) and the Common Gull (Larus canus) are considered as threatened species in Europe due to the rapid decline of their populations (SPEC 3, threat status D) (Gromadzki 2004); the Little Tern, the Ringed Plover (Charadrius hiaticula) and the Oystercatcher (Haematopus ostralegus) are listed in the Polish Red Data Book of Animals as species threatened with extinction. For all the species mentioned above, the islands in the Vistula river are the key breeding sites in Poland. They are used by 30-35% of the Polish population of the Ringed Plover and the Oystercatcher, and by 70-85% of the Little Tern and the Common Gull populations. They are also important breeding sites for the Common Tern (Sterna hirundo), the Little Ringed Plover (Charadrius dubius) and the Black-headed Gull (Chroicocephalus ridibundus) (10-35% of the Polish population, depending on the species)
All of these species have shown a clear decline over the last 2-3 decades. The most dramatic decline has been observed in the Common Gull population, which dropped by over 50% only in the last 15 years (1993-2008), with alarmingly low population parameters (high adult mortality and very low hatching success and chick survival). In addition, the Common Gull has disappeared (in fact, it went extinct) in many breeding sites that it had used in the Vistula valley. Although the status of other rare bird species in the Vistula Valley is not dramatic, it raises concern for the future, since between 1993-2009 the breeding success was very low and the population size decreased by 15-20% in the Ringed Plover and the Common Tern, by 20-25% in the Little Tern and by 30-40% in the Little Ringed Plover and the Black-headed Gull.
Similarly as in the rest of their breeding range, this difficult status of the birds of the Middle Vistula is mainly associated with the increased predation pressure by the American Mink (Mustela vison) and the Fox (Vulpes vulpes), and to a lesser extent by the Raccoon Dog (Nyctereutes procyonoides). An important threat is mass occurrence of midges (blood-sucking dipterans of the Simuliidae family) and nest trampling by cattle. An increasingly important problem is rapid overgrowing of important breeding sites of gulls, terns and plovers by willows, poplars and grasses, and in the case of the Common Gull, also the exceptionally low within-population genetic diversity of birds, causing high hatching failure and weak chick immunity.
View pictures illustrating project actions (Picasa)
Conservation measures
Without special conservation measures, to combat especially the mammalian predators, it will be difficult to halt the rapid decline of the numbers and, in the long term, also the extinction or disappearance of the Common Gull as well as other threatened species in the breeding sites in the Middle Vistula and in Poland. Given that, we launched a three-year comprehensive protection plan in the area that is central for these species. An advantage was that all the species that were covered by the active conservation measures had “common enemies”, used similar habitats and nested relatively close together. This enabled us to integrate treatments and cover nests or breeding sites of several species at a time. The protective activities were performed in a 120-km-long section of the Natura 2000 “Dolina Środkowej Wisły”, which consists of two sections of the Vistula: between Puławy and the mouth of the Pilica (km 371-457 of the river) and between Warsaw-Żerań and Zakroczym (km 522-555)
The detailed list of treatments was as follows:
- reduce the American Mink and Fox numbers by catching and euthanasia, and by shooting (Fox);
- neutralize the presence of terrestrial predators and cattle in breeding sites through electric fencing and, in the case of unprotected nests, by temporal clutch protection in incubators and replacing it with wooden dummy eggs;
- increasing the genetic pool in Common Gull colonies on the Vistula by exchange of broods between nests from distant breeding sites;
- organising collective pasturage and constant supervision of livestock on islands (cattle and horses), and mowing willows and poplars in the most important breeding sites of gulls and terns
Alongside these measures we performed current assessment of their effectiveness and a broad promotion, information and education campaign, both locally and nationally
The objective of these tasks was to:
- reduce the mortality of adult birds due to predation by terrestrial mammals
- reduce clutch and brood loss due to predation by terrestrial mammals, mass occurrence of midges and trampling of nests by livestock
- increase the hatching success and chick survival, mainly of gulls and terns
- reduce the numbers and activity of mammalian predators in the breeding sites in the Vistula riverbed
- increase the genetic diversity (= decrease the genetic similarity between individuals) in the colonies of the Common Gull
- restore habitats in the key breeding sites of gulls and terns
- increase awareness among local community and self-government authorities on the natural value of the Middle Vistula Valley and the purposes of the active conservation measures
If within three years the predation pressure by mammals ceases to be the fundamental cause of adult birds’ mortality in the Vistula breeding sites, and the breeding success of the protected species increases at least twofold, we will consider that the long-term objective of the project (halting the decreasing trend of threatened species) is possible to be achieved.
