| Summary: | The Corncrake is a threatened umbrella species for wet meadows, which mostly depends on managed grasslands. Therefore, effective conservation requires bird-friendly land management schemes and subsidies. Although the most important populations in Hungary usually breed in protected areas, some of these are regularly flooded, which forces Corncrakes to find breeding sites elsewhere. Such movements from protected/subsidised areas to suboptimal sites have risks for Corncrake populations and their conservation. Here, we describe a large-scale dynamic system of interlinked populations based on data from 4194 Corncrake territories found at four different sites (Aggtelek, Bodrogzug, Szatmár-Bereg and Zemplén regions) across eight years between 1997 and 2006 in NE Hungary (c. 1500 km2). The results showed that the total population fluctuated between 407 and 631 pairs and that the populations were more-or-less stable in the first four years (1997–2000). However, extended floods caused the disappearance of the species from the Bodrogzug region in 2005–2006, while in the other sites, the number of territories increased five-fold (Zemplén), three-fold (Aggtelek) and two-fold (Szatmár-Bereg). The correlation between the number of territories and maximum water level of river Tisza in April-May was negative in the Bodrogzug site and positive in the three other sites, indicating that interlinkages of the populations were associated with water levels. Our data thus support the hypothesis that many of the birds driven out by inundation of floodplain meadows moved to other sites in NE Hungary in flood years. These results suggest that even large, centrally located populations of Corncrake can be greatly exposed to risks of flooding and that it is highly important to maintain suitable alternative breeding sites for the species. The High Natural Value Areas programme may allow administrative and funding support to provide or extend protection and/or subsidies to maintain this large-scale dynamic system. To this end, the area managed in bird-friendly ways and subsidised under agri-environmental schemes was extended by 35,000 hectares in NE Hungary in 2009.
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