Long-tailed Duck Clangula hyemalis

During the late sixties and early seventies offshore surveys were undertaken in some parts of the Swedish waters using the boat patrols of the Swedish Coast Guard and aerial surveys (mostly by cooperation with the Swedish Airforce). The estimates presented in the Table for 1971-74 are based on these counts. The methods used at that time (without GPS etc) makes it a bit difficult to directly compare the results of the transects but a thorough re-analysis of the older data-set will be undertaken. Unfortunately the important offshore banks like the Midsjö Banks and Hoburgs Bank could not be covered at tehse surveys.

During the winters 1992 and 1993, the first ever total survey of the entire Baltic was undertaken, mainly using boat transects (Durinck et al. 1994) with aerial surveys in some areas.

In 2009, the Swedish offshore areas were more or less completely covered by aerial surveys for the first time. The only gap of importance for the Long-tailed Duck was the areas north of Gotland and around Gotska Sandön. These areas could however be covered in the winters 2010 and 2011. The total population of Long-tailed Ducks in Swedish waters in 2009 was estimated to be in the order of 0.5 milj. (see Table below). At the first ever total survey of the Baltic sea in 1992/93, the number of Long-tailed Ducks in Swedish waters was estimated to be in the order of 1.4 milj. Very large numbers were found on the offshore banks: Hoburgs Bank and Midsjöbankarna but also along the east coast of Gotland (see Table).

In 2010 and 2011 the major offshore banks were also covered by aerial surveys. In 2011 the survey could be considered as more or less complete as most areas that were not covered were totally frozen. Both 2010 and 2011 were harde ice winters (see map below for 2011) with many important areas for the species totally frozen. High numbers estimated for Hoburgs Bank in 2010 was certainly related to the ice-conditions along the Baltic coast, where important winter areas for the species were frozen. A similar situation was found for 2011, but in this year the number of Long-tailed Ducks on the Midsjöbanks was much lower than in the two previous winters.

A new all-Baltic survey was undertaken in the winter of 2016. The entire Swedish Baltic coast and the offshore banks in the economic zone were covered by line transects. In total 370000 Long-tailed Ducks were estimated to be present in the Swedish waters. As in the other years, the majority of the Long-tailed Ducks were found on the offshore banks (Hoburg and Midsjöbankarna) with 70% of the total for the country.

Some of he areas that could be covered in 2007 - 2011 were extensively surveyed during the 1960s and 1970s when duck counting started in  Sweden both using boat counts from Swedish Coast Guard patrols and aerial surveys (Swedish airforce).  The results from these surveys shown in the Table below indicate marked decreases for many important areas.

The offshore counts very clearly shows a very marked decrease in the population of Long-tailed Ducks wintering in Swedish waters since the 1992/93 survey: from 1,4 to less than 0,5 milj. individuals in 2009. The decrease has continued and hte estimate for 2016 was 370000, a 15 % decrease since 2009.

Overall the SOWBAS study in 2009 showed a decrease in the total population for the Baltic sea from 1992/93 to 2009 of about 60%. When it comes to the 2016 survey, the internatioanl results are not yet available.

Regional estimates of the number of wintering Long-tailed Ducks in Swedish waters