Call for 40th international Bewick’s Swan age count 11/12 December 2021 And results of the international age count: 12-13 December 2020

By Wim Tijsen, Kees Koffijberg and Preben Clausen

This synchronous international survey is part of the long-term monitoring scheme coordinated by the Swan Specialist Group, in order to assess annual productivity in the species. In 2020, the 39th age count was held in the weekend of 12-13 December. Data were received from ten countries and pointed out at 8.3% juveniles: a bit higher than in 2019, but still below the level that would be required to compensate for annual mortality rates. We hope that all countries, coordinators and observers will continue their contribution in this anniversary year for the 40th age count in this long term study to ‘keep a finger on the pulse’ of the Bewick’s Swan population.

December 2020; Bewick’s swans on the isle of Texel, Nths. Photo by Cor Fikkert

Since the early 1980s, the Swan Specialist Group has monitored the NW-European Bewick’s Swan population carefully, to keep track on the population status and assess its conservation requirements. For this purpose, an international counts of the population size is organised once every five years (last in 2020) and productivity is assessed on an annual basis. This setup is important because historically the population size was small and, following an increase in numbers between the 1970s and mid-1990s, is now in decline and subject to major changes in winter distribution. Indeed, having peaked at just below 30,000 birds in 1995, numbers dropped to 18,100 in 2010. Whether a slight recovery to c. 20,100 birds in 2015 (Beekman et al. 2019) has been maintained hereafter remains to be seen, pending on the final results of the 2020-census. Age counts are an important tool for understanding such fluctuations in population size, along with results of ring-readings which give insight in survival and mortality patterns (and changes in migration strategy).

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