Results of the December 2021 Bewick’s Swan age assessment, and a call for December 2022

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 2021, the 40th age count was held in the weekend of 11-12 December. Data were received from eight countries and resulted in 11.0% juveniles. This is 2% higher than in 2020, but still below the level that would be required to compensate for annual mortality. We hope that all countries, coordinators and observers will continue their contribution in this year’s 41th age count in this long term study to keep track on the wintering NW-European Bewick’s Swans.

Bewick’s swans in flight. Photo by Hans-Joachim Augst

2022 Age count

This year’s International age count will take place in the weekend of 17-18 December 2022. In most countries, this date also fits in the scheduled monthly waterbird count. Usually, by this time of the year, there is some information from the breeding areas. But, due to the international conflict between Russia and Ukraine and also because of the Covid-pandemic, field expeditions in the breeding area were not possible last summer. At least, reports of weather stations suggest that weather conditions in many parts of the Arctic were very warm. And the first impressions from arriving swan flocks in NW-Europe, and along the flyway, indicate an intermediate breeding season. Juvenile percentages for other arctic species such as Dark-bellied Brent Goose, Tundra Bean Goose and Greater White-fronted Goose even show pretty high values and suggest good breeding conditions. Hopefully the survey in December will point out what has been going on in the declining Bewick’s Swan population. We hope that all coordinators and organisations will continue their efforts in collecting these important data, which helps to understand the fluctuations and changes in the flyway population. We are very grateful to all those observers, coordinators and institutes for their efforts. The excel-sheet to collect the data for the international age count will be sent in a separate email to all coordinators.

Results from 2021 age counts

In December 2021, a total of 10,224 Bewick’s Swans was aged, which is a much larger sample (+8%) as in 2020 (Table 1). According to the latest results of the flyway population in January 2020 (Eileen Rees – in prep.) it means that we managed to check about 80% of the NW-European wintering population! The overall percentage of cygnets recorded was 11.0% in 2021 (compared to 8.3% in 2020). This is the highest juvenile count since 2013 (see below). Both winters were categorised as being very mild during the Mid-December counting period, although a cold spell was noticed in countries like Estonia, Lithuania and Latvia, where no birds were counted at all (cold spell in Poland as well, but still birds present, see below). Arrivals at the main wintering sites were rather late, which is more and more common due to the milder winters in NW-Europe (Nuijten et al. 2020) and which has been a driver for the meanwhile well-known north-eastward shift in the core wintering areas and increasingly large concentrations in Germany.

Read the full results here.