In October 2006 an individual of the Common Eider (Somateria mollissima) was examined and one female of Trinoton querquedulae was found on one of the remiges. This species of lice was recorded for the first time in Poland on the studied host. Up till now, T. querquedulae has been noted only on this duck species in Belgium. Considering the extremely scarce information available, this species of lice is most probably rare in the Common Eider.
In 1950s the Common Eider was a very rare species in the Black Sea region, migrating there only irregularly. A decade later, 9-14 males wintered in Black Sea bays. A few pairs attempted to breed there but their nests were flooded by storms. The first records (2 pairs) of successful breeding come from 1975. By the mid-1990s, the total number of breeding pairs had reached almost 1000.