The Aquatic Warbler LIFE Project – What have we achieved?
We have learnt about the exact habitat requirements of Aquatic Warblers and how to protect the species.
Every nature conservation project needs to be underpinned by sound science, in order to make sure that we can choose the right active measures, and that they really achieve, what they are designed to do.
This is why throughout the project we collected data on the number and distribution of Aquatic Warblers on all nine project sites. At these sites, we also systematically monitored changes in the key factors influencing the quality of Aquatic Warbler habitat:
- composition and structure of vegetation, where the birds feed and build their nests
- number and composition of insect and invertebrates, on which the birds feed
- water levels, which importantly influence vegetation and food availability as well as possible nest locations.
Additionally, we implemented several targeted studies, like a full inventory of all Aquatic Warbler sites in Poland in 2009 and studies to identify the exact parameters of an “ideal habitat”, which we could then apply to our project sites.
Very important was also a study on nesting productivity in relation to vegetation management. Analyzing all these data, we learned that every Aquatic Warbler site is different, and that there cannot be one type of management that fits all sites. Especially
differences in water conditions and nutrient availability decide, whether an area should be mown in summer or in winter, every year, every second year or maybe only once every 5-10 years.
All this knowledge we used to adjust the management we do on the sites and to develop management plans for each site. It also fed into new official Aquatic Warbler Species Action Plans for Poland and the German region of Brandenburg.
Thousands of hectares of delicate peat meadows need to be managed for the Aquatic Warbler each year in order to keep them open. Local farmers, who traditionally used to do this by hand, stopped doing this around the 70ies of the last century, when it became economically unattractive. Since then, these fen mires started to grow over with reeds or trees and bushes. We realised that it is not possible to re-introduce hand-scything on such a large scale, because of the forbidding costs and the fact that it would be impossible to find more than
a handful of people still ready to do this hard work. At the same time, extensive grazing with cattle or horses can also be a solution only for smaller areas. Therefore, within the project, we introduced a purpose-built prototype mowing machine. The machine is an adapted alpine piste-basher on caterpillar tracks – called “ratrak”, with very low ground pressure and fast working speeds (mowing 5-10 hectares per day, including removal of the vegetation mown). It also removes bushes and can be used during periods of high water and does not destroy the delicate peat soil and vegetation.
This solution was so successful, that ratraks are now used on all larger Aquatic Warbler sites in Poland. The idea is already being copied in Germany, Belarus and Lithuania.
Showing that it works!
Implementing conservation work on such a large scale, we need to make sure that the solutions employed do indeed achieve their aim, i.e. to an increase in good fen mire habitat and therefore in the population of Aquatic Warblers and the species that go with it.
When comparing the habitat quality before and after the project of the areas we have managed during the project with the models of ideal habitat that we created both for the Pomeranian Aquatic Warbler population and for the eastern Polish population, we can state that the very large majority of areas has improved considerably. Dense reed stands have become weaker and lower, bush overgrowth and thick litter layers of dead material have disappeared. However, such a clear trend can not yet be made out in the overall Aquatic Warbler population figures. With the
available monitoring techniques it is impossible to detect a statistically significant increase within just a few years from starting the management. We are waiting for the coming years to get a clear answer to this question.
The Polish population seems stable between 3200 and 3600 singing males, of these about 2,500 in the Biebrza Valley. Unfortunately, the situation looks still very worrying for the isolated Pomeranian population: here numbers have continued to decline – albeit slower – during the project period, from around 80 in 2003 to just around 55 singing males in 2011, with the species disappearing from its last site in Germany. There may just not be enough birds left to make use of the large areas of improved habitat in this area.
Things look much clearer if concentrating only on the areas managed within the project: In the so-called Bagno Lawki mire, the core area within the Biebrza Valley, Aquatic Warblers numbers have increased by 20% (almost 200 singing males) between 2005 and 2010 where management has been implemented, but stayed stable, where nothing was done. Altogether 336 ha of restored habitat has been re-occupied by the species at this site.
Numbers are also very promising for the new OTOP reserves in the buffer zone of the Biebrza National Park. Between 2005 and 2011, numbers of singing males increased from 5 to 21 in Lawki-Szorce and from 25 to 128 in Mscichy. Development of Aquatic Warbler numbers at Mscichy. Besides Aquatic Warblers, the most notable effect of the large-scale management was the return of large numbers of meadow-breeding waders to the mown areas, especially in the Biebrza National Park. Here, it was even possible to record the first breeding occurrences in Poland since 10 years for Wood Sandpipers and Jack Snipes.
One project alone cannot save a species, but it can make a beginning. Whether we can save the Aquatic Warbler and even increase their numbers, depends on further action and cooperation of local farmers, conservation authorities and private organisations with the support of the wider public that appreciates these efforts. The Polish and the Brandenburg Aquatic Warbler Species Action Plans and the local site management plans need to be implemented. One element of this is the development of biomass use for energetic purposes that could ensure future financing for ongoing management. OTOP is already implementing another project with this aim. In the mean time, the Polish government needs to ensure the continuation and further improvement of the successful agri-environment schemes that help fen mires. Regular monitoring will be continued to observe the effects of the work on Aquatic Warblers. But in order to significantly increase the population of Aquatic Warblers and to remove the tag “globally threatened” from the species, it will not be enough only to improve existing breeding sites. It is necessary to restore long-lost sites, mires drained for peat extraction or agriculture, which may have now lost the economic importance they had when freshly drained. We also need to observe the development of the Pomeranian population. Should it continue to decline despite of good habitat available, it might need to be considered to strengthen this population with individuals derived from the stronger eastern population.
