Red-breasted Merganser Mergus serrator

The breeding range of the Red-breasted Merganser covers most of Sweden, the species breeding both on coastal sites and on inland lakes from the south to the Scandinavian mountain chain. During the winter it is mainly a marine species occurring especially along the open coasts of the country but is also seen in the archipelagos. The species is wide-spread and often seen far out at sea, mostly in small groups and is difficult to survey. The winter population in the country in normal years is probably between 5000 and 10000 for the Baltic and the Kattegatt with additional numbers wintering in Bohuslän on the west coast. It is found in the same areas during the autumn period. Later counts in the southern part of Öresund and off Falsterbo indicates that the total winter population might be considerably larger.

Midwinter indices for the Red-breasted Merganser show a significantly increasing trend over the years, especially until the cold winter of 1987. The level was lower during the first years of the 1990s but increased again to the highest value then noted in January 2000, but January 2001 produced an even higher index, the following winters showed  lower winter indices. A small upward change was noted between 2007 and 2008. The cold winters 2010 and 2011 showed lower indices.

September counts on the sample sites are relatively low but allow the calculation of annual indices. Not unexpectedly from the small numbers counted marked fluctuations are found between years, but the trend over the series is significantly decreasing at least until 1998. There was some increase between 1998 and 1999 followed by a marked increase to September 2000, when the index was at the same level as at the start of the counts. The four following years had lower indices but then 2006 had the next highest septemberindex for the species. The increase in September index continued and 2008 was the highest index in the series, but in the following years the indices were back to normal. The total number of Red-breasted Merganser counted is however small so wide variations are to be expected.