Is thiamine deficiency a significant cause of declining bird populations in the Baltic Sea Region?

NEWS | 2013-11-08

The Swedish Agency for Marine and Water Management (SWAM) commissioned Mistra EviEM to evaluate the current understanding of the link between a lack of vitamin B1 (thiamine) and the declining bird populations in the Baltic Sea region. Thiamine is essential for many organisms because it is involved in several basal metabolic processes. According to EviEM’s pilot study, current scientific evidence for the thiamine deficiency hypothesis is insufficient for conducting a systematic review.

Paralysed sea gull in Ronneby archipelago. Photo: Le Carlsson/TT bild

Since the early 2000s, the number of dying and dead seabirds along the Baltic Sea coast has increased. These birds often show paralysis syndrome, which has become known as “bird death”. But why the birds die is still not known. One existing hypothesis is that the lack of thiamine causes bird death in a similar manner as the disease M74 affects salmon populations in the Baltic Sea. On behalf of SWAM, Mistra EviEM investigated the requirements for carrying out a systematic review on whether thiamine deficiency in birds could be a major cause of the widespread and severe reduction in bird populations in the Baltic Sea over the past decade. Among the bird species that are declining, scientists have found thiamine deficiency in herring gulls and eiders.This pilot study revealed that even if scientists could have shown that various birds in the southern part of the Baltic coastline have low levels of thiamine, it is still unknown whether paralysis symptoms in birds are mainly caused by the lack of this vitamin.

Additional studies are therefore needed to find out whether or not there is a causal relationship between thiamine deficiency in birds and the declining bird populations in the Baltic Sea region. The lack of evidence also means that this issue requires more research before a systematic review can be considered feasible.